Subway’s Sweet Onion Sauce

When I posted about my plans to recreate Subway’s best recipes, everyone seemed to be the most excited about their sweet onion sauce. It’s cheap, quick and delicious on sandwiches, salads and anything you want to add sweet kick to.

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 sandwich repertoire and it couldn’t be easier to make. It’s just a bonus that it doesn’t have any funny preservatives.

This recipe is part of a series recreating all the best recipes from Subway. You can find this mega-post here.

sweet onion sauce
Southwest Sauce (Front), Chipotle Southwest Sauce (Left), Mayonnaise (Right)

Equipment Needed

Usually I have some recommendations on how to make my 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.

Subway’s Sweet Onion Sauce

A perfect recreation of Subway's sweet onion sauce
Course Side Dish
Cuisine American
Keyword subway sweet onion sauce
Cook Time 10 minutes
Resting Time 6 hours
Total Time 6 hours 10 minutes
Servings 16
Calories 42kcal


  • 2/3 cup sugar granulated
  • 1/2 cup cold water
  • 6 tbsp vinegar white or distilled
  • 1 1/2 tbsp red wine vinegar
  • 1 tbsp cornstarch or arrowroot powder
  • 1 tbsp minced onion flakes
  • 2 1/2 tsp dijon mustard
  • 2 1/2 tsp mustard powder
  • 3/4 tsp celery salt
  • 3/4 tsp fresh onion juice use a garlic press to juice
  • 1 tsp poppyseeds
  • 1/2 tsp onion powder
  • 1/4 tsp garlic powder
  • 1/2 tsp salt
  • 1/3 tsp paprika
  • 1/4 tsp 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.


Calories: 42kcal | Carbohydrates: 9g | Protein: 1g | Fat: 1g | Saturated Fat: 1g | Sodium: 191mg | Potassium: 7mg | Fiber: 1g | Sugar: 8g | Vitamin A: 24IU | Vitamin C: 1mg | Calcium: 4mg | Iron: 1mg

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