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.
Equipment Needed
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!
📖 Recipe
Subway's Sweet Onion Sauce
Ingredients
- 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
Instructions
- 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.
Beth Sachs
I LOVE their sweet onion sauce. So glad I now have the recipe to use at home!
Maritime Glutton
Thank you so much, Beth! I hope you love it 🙂
Mai
Interesting to know what's in the Subway sweet onion sauce.
Maritime Glutton
It's so easy to make! Hope you love it, Mai!
Beth
This looks so delicious and flavorful! I can’t wait to give this a try! My hubby is going to love this recipe!
Maritime Glutton
Thank you Beth! I hope you and your husband love it <3!
Gita
This is great! We're always trying to replicate our beloved restaurant sauces and seasonings, so we'll definitely be trying this one out!
Maritime Glutton
Thank you so much, Gita! I hope you love it
Jenn
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!
Maritime Glutton
I have up fast food this year so I totally relate Jenn! I hope you love it 🙂
Shadi Hasanzadenemati
Love how easy this recipe is. It’s perfect for our family!
Maritime Glutton
Thank you so much Shadi! It’s amazing how easy it is.
Shadi Hasanzadenemati
My family is going to love this, thank you for the recipe!
Danielle Wolter
This sounds delicious! It's so easy and everyone is going to love it!
Maritime Glutton
Thank you so much, Danielle! Hope you love it
Whitney
I don't mind all the ingredients because this is such a good sauce! Perfect for a juicy burger off the grill!
Maritime Glutton
Thank you so much Whitney! I'm so glad you liked it 🙂
WILLIAM COUSERT
Does anyone know if there are any close copies to Subway's Sweet Onion Sauce that are available in your local grocery store?
Maritime Glutton
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!
Terry
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.
Lauren
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 🙂
Darian
Terry, it's a decent copycat. I can taste some similarities. I think what also helps is a bit of lemon or lime juice.
Lauren
Thanks so much for the feedback Darian 🙂
DispatchMinion
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?
Lauren
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 🙂
Blake
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!
Lauren
I'm so glad you liked it, Blake 🙂
Ben
Thanks for putting the time in to make this recipe, I can't wait to keep a bottle of this stuff handy! 🙂
Lauren
Can’t wait for you to try it! 🙂
TK
Do you use regular onions, red onions, or sweet maui onions?
Lauren
Hi Treevis! I’d recommend white, yellow or sweet onions 🙂
Mike
Tastes like crap
Lauren
Hi Mike - can you tell me what the issue is so I can maybe help you troubleshoot? 🙂
Janice
This is mustard sauce. Not sweet onion.
Lauren
Hi Janice! This is definitely sweet onion sauce but feel free to reduce or leave out the mustard powder if you find it overpowering 🙂
Diana
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?
Lauren
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 🙂