Don't be overwhelmed by the large ingredient list, this sweet onion sauce takes less than 15 minutes of work for a condiment that lasts almost forever. It's a great addition to anyone's sandwiches and it couldn't be easier to make. It's just a bonus that it doesn't have any funny preservatives. This recipe was created by trialing and taking bits from both this and this recipe. The recipe from The Spice Guru made an incredible base recipe, though it was too sweet and too salty - the changes have improved on their already very strong recipe.
This recipe is part of a series recreating all the best recipes from Subway. You can find this mega-post here.
Usually I have some recommendations on how to you can make recipes easier with my favourite kitchen tools, but for this, all you really need is a pot (small in size is fine) and a whisk. For a bit of an easier time, a garlic press is recommended, but you can use a cheese grater for grated onion if you don't have a garlic press or juicer to extract onion juice.
The only hard part about this recipe is being able to wait for it to reach optimal flavour during the 6 hour rest time. It smells amazing when you're making it but trust me, you want to let it rest for the best taste.
Sweet Onion Sauce Ingredients
With a whopping 17 ingredients, this recipe may seem overwhelming, but there's only one ingredient found outside a spice cabinet or pantry. The less common ingredients like sesame oil and poppyseeds may not be in every household, but they last forever.
The only non-shelf stable ingredient is onion juice, which comes from taking an onion through a juicer (or preferably a garlic press) to get the flavour but not the texture. As mentioned above, you can grate the onion instead if you don't mind a slightly stronger and milled onion taste/texture.
Other Sauce Recipes
- Donair Sauce
- Taco Bell Quesadilla Sauce
- Subway Mayonnaise
- Subway Chipotle Southwest Sauce
- Zero Waste Pesto
Have you tried this recipe? Leave me a 5 ⭐️ rating in the recipe card! I love to hear from you! You can also follow me on Instagram, Facebook, Pinterest, and Twitter, and sign up for my newsletter!
Subway's Sweet Onion Sauce
- ⅔ cup sugar granulated
- ½ cup cold water
- 6 tablespoon vinegar white or distilled
- 1 ½ tablespoon red wine vinegar
- 1 tablespoon cornstarch or arrowroot powder
- 1 tablespoon minced onion flakes
- 2 ½ teaspoon dijon mustard
- 2 ½ tsp mustard powder
- ¾ teaspoon celery salt
- ¾ teaspoon fresh onion juice use a garlic press to juice
- 1 teaspoon poppyseeds
- ½ teaspoon onion powder
- ¼ teaspoon garlic powder
- ½ teaspoon salt
- ⅓ teaspoon paprika
- ¼ teaspoon black pepper
- 1 - 2 drops sesame oil
- In a small pot, whisk together all ingredients over medium high heat - allow to bring to a boil while whisking constantly.
- Reduce heat to low and simmer, stirring until thickened - around 5 minutes.
- Allow to cool in the refrigerator overnight.
- This sauce keeps indefinitely if stored in a sealed jar in the fridge.
I LOVE their sweet onion sauce. So glad I now have the recipe to use at home!
Thank you so much, Beth! I hope you love it 🙂
Interesting to know what's in the Subway sweet onion sauce.
It's so easy to make! Hope you love it, Mai!
This looks so delicious and flavorful! I can’t wait to give this a try! My hubby is going to love this recipe!
Thank you Beth! I hope you and your husband love it <3!
Thank you for this recipe! Seriously life changing for me 🙏
This is great! We're always trying to replicate our beloved restaurant sauces and seasonings, so we'll definitely be trying this one out!
Thank you so much, Gita! I hope you love it
The sweet onion sauce was always my favorite part of a sub - I'm so excited to be able to make this at home now that there's no Subway near me! Yay!
I have up fast food this year so I totally relate Jenn! I hope you love it 🙂
Carole A Dennis
Thank you so much for the recipe. I love the sweet onion sauce and am total bummed they have replaced it with teriyaki sweet onion sauce. Total ruined my tuna sandwich. Will try this soon and will give a rating then.
Love how easy this recipe is. It’s perfect for our family!
Thank you so much Shadi! It’s amazing how easy it is.
My family is going to love this, thank you for the recipe!
This sounds delicious! It's so easy and everyone is going to love it!
Thank you so much, Danielle! Hope you love it
I don't mind all the ingredients because this is such a good sauce! Perfect for a juicy burger off the grill!
Thank you so much Whitney! I'm so glad you liked it 🙂
Does anyone know if there are any close copies to Subway's Sweet Onion Sauce that are available in your local grocery store?
Hi William! The closest I've tried is Renees Sweet Onion Vinaigrette, but I still prefer this version 🙂 If I'm feeling lazy it's an okay substitute though!
Also. Ken's steakhouse brand has a sweet Vandalia onion sauce that tastes pretty close but has chunks on onion in it
Wow, all these comments on how it looks great but no one has tried it? Looking for some solid comments on how this recipe tastes.
I love it and find it almost identical! I quite fast food this year for a resolution and have used this a few times to itch the craving. Would love to hear from you if you make it 🙂
Terry, it's a decent copycat. I can taste some similarities. I think what also helps is a bit of lemon or lime juice.
Thanks so much for the feedback Darian 🙂
I am going to make this my next day off! What volume of liquid is there at the end so I know what size squeeze bottle to get?
It will depend how much you reduce the sauce 🙂 I used a 7.8 ounce squeeze bottle and there was a bit of head space 🙂
Amazing recipie! Very quick and easy. If it seems too thin just simmer longer. It tastes just like subways. I use it as a base for sauce and marinades. Add lime juice for a Mexican twist or sriracha for some spice!
I'm so glad you liked it, Blake 🙂
Thanks for putting the time in to make this recipe, I can't wait to keep a bottle of this stuff handy! 🙂
Can’t wait for you to try it! 🙂
Do you use regular onions, red onions, or sweet maui onions?
Hi Treevis! I’d recommend white, yellow or sweet onions 🙂
Tastes like crap
Hi Mike - can you tell me what the issue is so I can maybe help you troubleshoot? 🙂
This is mustard sauce. Not sweet onion.
Hi Janice! This is definitely sweet onion sauce but feel free to reduce or leave out the mustard powder if you find it overpowering 🙂
I was very excited when I saw this but was worried with how much vinegar was going in because the original recipe doesn't have any taste of vinegar in it to me. I made it anyway in the hopes that the other flavors/cooking would remove the taste. But the vinegar taste remained and it powerful.
Any recommendations? Should I do half the amount of the vinegar and see if that makes a difference? Has anyone else had this experience?
Hi Diana! The third ingredient in Subway's sauce on their website is corn vinegar! There definitely is vinegar and quite a bit of it compared to other ingredients. If you find it's too strong, check out the kind of vinegar you're using - maybe you just aren't a fan of overly vinegary foods. Maybe try reducing the vinegar by about 25% and replacing that with water.
Hope you find a way to make it work for your tastebuds 🙂
How can I rate this 10 STARS???
bless your heart for sharing this!!!
I thank you, my son thanks you, my mom thanks you and several of my friends who has tried it thank you.
I want to thank you AGAIN!
This is so good! I've always enjoyed a good sandwich and use to enjoy subway until they started using a certain pink hair soccer person on their commercials. Any company that uses a person who kneels during our country's NATIONAL ANTHEM to promote their products I will do all I can not to buy anything from them so it's been a long time since I've had sweet onion sauce.
Thank you again for sharing.
Within a week I've made this 3 times.
People if you like sweet onion sauce look no further..
I even put it on a pulled pork sandwich!
French fries and chicken wings may be next!
So glad you and the taste-testers liked it, Troy! 🙂
Just made this recipe for the first time and this recipe is EXACTLY like the sweet onion at Subway. I didn’t do a side by side taste test but I’m usually very picky about my sauces and this one is GOOD! I’m gonna make this 100 more times. So delicious! Thank you for the recipe!!
Thank you so much for the feedback Kaoutar! I'm so glad to hear you liked it 🙂
This is a lifesaver it’s the only sauce anyone in our family added to our subs Now that Subway has changed the ingredients and added teriyaki to the sweet onion sauce we haven’t been back! Made your recipe and everyone was so impressed (family picnic of 12-15) everyone voted definitely 5 stars. I did substitute Splenda for white sugar and can’t seem to find how to recalculate the nutrition facts any suggestions
Very nice alternative to the original. Thanks for sharing 5 stars
Awesome sauce! I used to love roast beef sandwiches with sweet onion sauce, and subway stopped serving roast beef. But now I can get a sandwich from anywhere, and use this amazing sauce to make it perfect! My husband wants to try it on lots of other things - spring rolls, etc. I didn't have the celery salt or poppy seeds, and it was still fantastic! Thanks for a great recipe!
I'm so glad you loved it, Renee 🙂 Thank you for the kind feedback!
We love love it! My husband and I love Subway sweet onion sauce! We get the same sandwich every time we go.
Chicken Teriyaki with sweet onion sauce... so one day, I was looking up copycat recipes online. I saw this one, made it last night.. made chicken sandwiches with all the trimmings with this sauce..My husband's exact words...
Well, there's no sense in going to Subway anymore! His comment made my heart smile! This copycat recipe came as close as you can get, if not, spot on! Thank you!
This is such a wonderful comment Tracie - thank you so much for sharing with me <3
Can you double or triple this recipe?
You can! Just double/triple all ingredients and follow the recipe!
I haven’t made it yet but if it keeps indefinitely why not make more.
I find this a good amount 🙂 You're welcome to make more, but like most foods, even if it doesn't go bad it's the best when it's fresh. It's easy to make so I make it fresh when I want it!
This recipe is so good, my hubby and I love it so much thanks heaps
So glad to hear you and the hubby approve! Thanks for the comment Rachel 🙂
You nailed it, Lauren. Made this today and was lucky to have all of the ingredients on hand.
I'm so happy to hear that - thank you for the feedback!
I love soccer sweet onion sauce subway
I'm not sure why, but mine turned out too thick and has a bitter after taste, I don't like it. But I thought maybe I burnt the sugar? Like bitter toffee
Hey Emma, it definitely sounds like you may have burnt it. You really just want to cook it long enough to melt the sugar and incorporate everything 🙂
I done a side by side test with the subway sauce and your recipe
It's the same, everyone at home agrees
Your amazing, I can't wait to try more of your recipes, I'm sure they'll be tasty
Thank you for the kind words Emma! I'm so glad to hear it was a hit 🙂
Absolutely delicious and easy to make! I would definitely recommend this recipe.
Now that I have all the ingredients, am going to make it today..that was the sauce that my husband loved, and they discontinued it in favor of another sauce...I bought bottles at Walmart for $1.97 just for this purpose, as I make sub sandwiches for our sunday lunch...
I am roughly one year deprived of The Sauce since Subway foolishly discontinued it last year and just now, a few minutes ago, I taste-tested my first batch of this recipe. I made some minor changes (didn't want to buy mustard powder so i just stirred in like half a teaspoon of regular-ol-mustard, didn't have a way to juice the onion or any flakes so I just... grated some onion on the roughest side of my cheese grater, a task I recommend doing with your eyes closed) and THIS. THIS IS THE STUFF! Thank you, wonderful stranger. This is getting a dedicated squeeze bottle in the fridge.
I'm so happy to hear that, Mags! Thank you for the kind review 🙂
This is absolutely spot on. I love it!!!
I'm so glad to hear Teddy!
This looks lovely and I can't wait to make it but I need to ask a stupid question. I went to order the minced onion flakes but it came up with three different items, like onion granules, dried crispy onions (like the salad toppings) and fresh minced onions. Could someone please let me know which I'm meant to be using? Thank you in advance!
Hi Sarah, you would use the dried minced onion. It's similar to onion powder but it isn't a powder. It's dried flakes of onion 🙂