Chinese Sweet and Sour Sauce with Brown Sugar

1/3 cup white vinegar
4 TB brown sugar
1 TB ketchup
1 tsp soy sauce
 
Mixture:
2 teaspoons cornstarch mixed with 4 teaspoons water

Directions
Mix the vinegar, brown sugar, ketchup, and soy sauce together and bring to a boil in a small pot. 
Mix together the cornstarch and water, add to the other ingredients and stir to thicken.

If desired, you can add 1 green pepper, cut into chunks, and pineapple chunks as desired after adding the cornstarch. 
For a thicker sauce increase the cornstarch to 4 teaspoons while keeping the water constant.