Heat the tomato sauce in a saucepan on a stove-top burner's low setting. Pour 1 tsp. of vinegar or lemon juice into the sauce and stir the mixture until the liquid until you completely combine the liquid. Taste the sauce to determine if the sauce is less sweet.Add additional vinegar or lemon juice 1 tsp. at a time until the sugar taste is neutralized to your liking.eat the tomato sauce in a saucepan on a stove-top burner's low setting. Pour 1 tsp. of vinegar or lemon juice into the sauce and stir the mixture until the liquid until you completely combine the liquid. Taste the sauce to determine if the sauce is less sweet.