Drain pineapple juice into a small bowl.

Add teriyaki sauce to the pineapple juice.

Place 3 tablespoons of the teriyaki mixture in a resealable plastic bag.

Add pineapple slices to the bag and rotate to coat them with the sauce.

Set the pineapple aside to marinate.

Shape ground beef into four patties.

Place the patties in an 8-inch square baking dish.

Pour the remaining teriyaki sauce mixture over the patties.

Marinate the patties for 5-10 minutes, turning once.

In a skillet, sauté sliced sweet onion in butter until tender, about 5 minutes.

Grill or broil the burgers until they are no longer pink inside.

Place the pineapple slices on the grill or under the broiler to heat through.

Layer lettuce and sautéed onion on the bottom halves of the toasted buns.

Top with the grilled burgers, Swiss cheese, grilled pineapple slices, and cooked bacon strips.

Replace the top halves of the buns and serve immediately.