Preheat oven to 325 degrees. In a 2 quart casserole, combine baked beans, onion, ketchup, brown sugar, pickle juice, mustard, molasses, and vinegar. Bake, uncovered, for 1 1/2 hours.
Partially cook bacon to remove some of the fat. Drain bacon on paper towels, discard drippings. Place bacon on top of bean mixture. Bake uncovered for 15 minutes more. Let stand for 15 minutes before serving.