Drain pineapple; reserve syrup. Combine syrup, brown sugar, 3 Tbsp teriyaki sauce, vinegar and ketchup; set aside.
Mix beef with remaining 2 Tbsp teriyaki sauce and onion; shape into 20 meatballs. Brown meatballs in large skillet; drain off excess fat. Pour syrup mixture over meatballs; simmer 10 minutes, stirring occasionally.
Dissolve cornstarch in water; stir into skillet with pineapple. Cook and stir until sauce thickens and pineapple is heated through.
Servings: 6 to 8