I was skeptical at first about a hamburger without a bun...but these burgers need no bun! There is so much sweet goodness going on, they can stand all by themselves. Even my 2 and 4 yr old (who wouldn't eat a regular hamburger to save their lives) absolutely love these.
For hamburger patties: combine the ground beef, onion, cracker crumbs, and salt. Form into 6 patties.
Brown the patties in a small amount of oil in a large skillet.
While hamburgers are browning, drain the pineapple juice from the can into a sauce pan. Reserve the pineapple chunks for later. Add the corn starch, vinegar, brown sugar, and soy sauce to the sauce pan. Cook, stirring until sauce thickens and bubbles, about 5 minutes.
Once the hamburgers are browned on both sides, add the thickened sauce to the pan along with the reserved pineapple chunks. Cover pan and simmer for 15 minutes until hamburger patties are cooked through. Serve with sauce and pineapple chunks drizzled over the tops of the patties.