Gather the ingredients for this recipe so you have everything on the counter or table.
Prepare the Ingredients
Rinse and drain 15 oz. kidney beans in a colander.
Using a sharp knife and cutting board, mince 1 cup sweet onion.
Make the Salad
Place 10 oz. frozen mixed vegetables in a medium glass bowl and microwave on high for 3-5 minutes until crisp-tender.
Stir in the kidney beans and minced onion.
Prepare the Sweet and Sour Sauce
In a small saucepan over medium heat, bring 3/4 cup granulated sugar, 1/2 cup apple cider vinegar, and 1 tablespoon cornstarch to a boil, whisking constantly until thickened.
Let cool for 5 minutes and pour over vegetables. Season with 1/2 teaspoon kosher salt and 1/2 teaspoon freshly ground black pepper. Toss to combine. Refrigerate for 2-4 hours. Serves 4-6.