Combine pineapple syrup with chicken broth, brown sugar, vinegar, soy sauce, catsup and cornstarch. Cook, stirring, until thickened. You can refrigerate the sauce as much as a day ahead.
Shortly before you want to use the sauce, heat it slowly, stirring until bubbly. Add onions and peppers, pineapple chunks and cooked meatballs. Heat for 30 minutes or more.
Can be served on a bed of rice or as appetizers.
Makes about 2 1/2 cups liquid sauce (plus vegetables and fruit).