Mix the raw meat, onions, garlic, and soy sauce in a bowl. Cover and marinade in refrigerator for 30minutes. Form meat into patties and grill until cooked through. Grill sliced pineapple with the meat until heated through and tender. Meanwhile, in a large nonstick skillet, sauté onion and bell pepper until very tender. To serve, top burger with a pineapple ring and sautéed vegetables.