Chow.com and Betty Crocker both publish simple and easy to follow sweet-and-sour sauce recipes. Betty Crocker's version includes a few vegetables, while Chow's is simpler.
To make Chow.com's sweet-and-sour sauce, combine 1/4 cup lightly packed light brown sugar, 1/4 teaspoon salt, 1 tablespoon ketchup, 1 tablespoon light soy sauce, 3 tablespoons unseasoned rice vinegar and 1/2 cup water in a saucepan. Bring to a boil over medium heat while stirring to dissolve the sugar. Dissolve 2 teaspoons cornstarch in 2 tablespoons water, and add it to the saucepan. Continue to cook for 15 seconds or until the sauce thickens to a desired consistency. Remove from heat, and let cool. Add extra salt to taste, if desired.
To make Betty Crocker's sweet-and-sour sauce, mix 1/2 cup packed brown sugar and 1 tablespoon cornstarch. Drain 8 ounces of crushed pineapple in juice, and retain the juice. Add enough water to the pineapple juice to measure 1/2 cup. Add the juice to the sugar mixture, and add 1/3 cup white vinegar and 1 tablespoon soy sauce. Heat to boiling while stirring. Boil and stir for one minute. Add crushed pineapple and 1/4 cup finely chopped green pepper. Stir, and use immediately, or cover and refrigerator for up to two weeks.