Cook and stir bacon and onion together in skillet over medium heat until bacon is partially cooked, 5 to 10 minutes. Add celery to bacon mixture and cook until bacon is cooked but not crispy, about 5 minutes more.
Combine bread cubes, bacon mixture, and garlic salt in a large bowl; pour into a 9x13-inch baking dish. Pour apple juice and butter over bread cubes.
Bake in the preheated oven until heated through and lightly browned, about 15 minutes.