In 2-quart (8 x 8) baking dish, combine soy sauce, sugar, onions, ginger and garlic; mix well.
Shape beef into 4 patties.
Add to soy sauce mixture, turning over to coat.
Cook uncovered, 6 minutes or until done, turning once during last half of cooking time.
Top with pineapple slice and cook uncovered, 30 seconds to warm pineapple.