Easy Subway sweet onion sauce recipe made from scratch within 15 minutes. If you love sweet onion sauce at Subway, this recipe is for you!

The recipe I am sharing is very close to what you would get at the Subway restaurants. It has the perfect balance of sweet and tangy flavors. I always make this condiment to pair my Subway style dinner – especially with chicken teriyaki sandwiches.
This easy, inexpensive, homemade Subway’s sweet onion sauce recipe is so useful when you are at home and want to enjoy a copycat subway experience.
This sweet onion sauce is
- vegan
- gluten-free
- preservative-free
- oil-free
- & kid-friendly
What to eat with Sweet Onion Sauce
There are various ways it can be served.
- Spread: Use It as a spread on bread or your favorite sandwiches.
- Salad dressing: Drizzle on salad to give it a flavor boost
- Dipping sauce: Excellent dipping sauce for roasted, grilled, or fried veggies, fish, or chicken.
- Marinade: Use as a marinade for meat, chicken, fish.
I also love using mine with chips, french fries, baked potato, paratha, and pita bread. Here are some of the great recipes that work with sweet onion sauce.
- Paneer Pakora
- Aloo Bonda
- Grilled Potato wedges
- Mirchi Vada
- Paneer Potato Balls
- Chicken Fry
- Gobi Pakora
- Watermelon Mango Salad
Is this Sweet Onion Sauce Healthy?
It is a far better alternative than store-bought sauces in terms of fat and sodium content. But it contains sugar. So, eating moderately is usually fine.
Sweet Onion Sauce Ingredients
The ingredients used in this sauce are simple and fresh. Once you have got all the ingredients ready it just takes minutes to come together. Here’s all you need:

- Onion: any sweet variety; Some popular sweet onion varieties include Walla walla, Texas sweets, Maui, and Vidalia. White or yellow onion will work as well.
- Garlic: just a touch, to enhance the flavor;
- Vinegar: plain white distilled vinegar and balsamic vinegar;
- Granulated Sugar: you can also use brown sugar;
- Cornflour: cornflour or cornstarch to thicken the sauce;
- Black pepper powder: freshly ground is best;
- Nigella seed(also called kalonji): available in Asian grocery stores. Tastes like oregano and onion mix. It adds a hint of extra flavor. I like the flavor but you can totally choose to skip it;
- Lemon juice: fresh;
- Salt: regular table salt;
- Water: cold filtered water;
Preparations Step By Step
- Peel the onion and garlic, roughly chop them, and blend until look smooth. Squeeze the juice using a muslin cloth and transfer to a pan or pot.
- Heat up the pan. Add in water along with sugar, salt, white vinegar, balsamic vinegar, black pepper, nigella seeds, and bring the mixture to a boil until sugar dissolves.

- Whisk ¼ cup water and cornflour together in a bowl, and make a slurry.
- Add in cornflour slurry and stir continuously over medium flame until the sauce thickens and looks glossier.
- Remove from heat and add lemon juice. Stir to mix and allow the sauce to come to room temperature.
- Store in an airtight container in the refrigerator and use when needed.

How to store
Let it cool, then transfer to an airtight container and refrigerate for up to 5 days.
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Subway Sweet Onion Sauce Recipe
INGREDIENTS ( 1 CUP = 240 ML )
- 1 medium-size onion
- 2 garlic cloves
- ¾ cup water plus ¼ cup water
- ⅓ cup granulated sugar
- 1 tsp balsamic vinegar
- 1 tsp white vinegar
- ¼ tsp nigella seeds/kalonji
- ¼ tsp black pepper, freshly ground or to taste
- ¼ tsp salt or to taste
- 2 tsp cornflour
- ½ tsp lemon juice, fresh
INSTRUCTIONS
- Peel the onion and garlic, roughly chop them, and blend until look smooth. Squeeze the juice using a muslin cloth and transfer to a pan or pot.
- Heat up the pan. Add in water along with sugar, salt, white vinegar, balsamic vinegar, black pepper, and nigella seeds. Bring the mixture to a boil until sugar dissolves.
- Whisk ¼ cup water and cornflour together in a bowl, and make a slurry.
- Add in cornflour slurry and stir continuously over medium flame until the sauce thickens and looks glossier.
- Remove from heat and add lemon juice. Stir to mix and allow the sauce to come to room temperature.
- Store in an airtight container in the refrigerator and use when needed.
Notes
- Onion: any sweet variety; Some popular sweet onion varieties include Walla walla, Texas sweets, Maui, and Vidalia. White or yellow onion will work as well.
- Garlic: just a touch, to enhance the flavor;
- Vinegar: plain white distilled vinegar and balsamic vinegar;
- Granulated Sugar: you can also use brown sugar;
- Cornflour: cornflour or cornstarch to thicken the sauce;
- Black pepper powder: freshly ground is best;
- Nigella seed(also called kalonji): available in Asian grocery stores. Tastes like oregano and onion mix. It adds a hint of extra flavor. I like the flavor but you can totally choose to skip it;
- Lemon juice: fresh;
- Salt: regular table salt;
- Water: cold filtered water;
Sudhir sarkar
Excellent
Geetanjali
Thank you!
Anaiah
This sweet onion sauce was so flavorful and quick to make!
Alexandra
What a delicious sauce – full of flavour.
Kylie
Yum! We really enjoyed this!
Ramona
This was good!! Will definitely make it again!
Alice | SkinnySpatula
Looks smashing! I love that sauce at Subway and yours looks just like it.
Kristina
A great alternative to the real thing, only I suspect this one has way more “fresh” and “natural” ingredients. Thanks for sharing this!
Pam
I use this on everything!
Kayla DiMaggio
This was so good that I bookmarked it! I love Subway’s sweet onion sauce and I get it everytime. Now I know how to make it from home!
Sue
My favorite sauce from Subway!
Oscar
Great recipe
Ksenia
Finally, one of my favourite sauce is revealed!
Mihaela|https://theworldisanoyster.com/
I had no idea it was so easy to make!