1 can (8 ounces) sliced pineapple
3/4 cup teriyaki sauce
1 pound ground beef
1 large sweet onion, sliced
1 tablespoon butter
4 lettuce leaves
4 sesame seed or onion buns, split and toasted
4 slices Swiss cheese
4 bacon strips, cooked

Drain pineapple juice into a small bowl; add teriyaki sauce. Place 3 tablespoons in a resealable plastic bag. Add pineapple; toss to coat and set aside.
Shape beef into four patties; place in an 8-in. square baking dish. Pour the remaining teriyaki sauce mixture over patties; marinate for 5-10 minutes, turning once.