These are really simple and good

1 lb. ground beef
2 slices bread, crumbled
1 egg
1 medium onion, chopped
1/2 cup ketchup
2 Tbsp. mustard
2 Tbsp. vinegar
2 Tbsp. Worcestershire sauce
1/4 cup brown sugar
Mix together beef, bread, egg, and onion. Shape into balls about the size of a quarter. Mix remaining ingredients and pour over meatballs. Bake in a 350 degree oven for 30 to 35 minutes.