Hamburger Barbecue on a Bun/ aka Sloppy Joes

This BBQ on a bun has a different flavor but I like it! In fact it is the only BBQ on a bun that my sister will eat!

1 C. Ketchup
1 C. Water
2 TSP. Mustard
1 TBSP. Vinegar
2 TSP. Chopped Onion
1 to 1 1/2 lb. Hamburger
Salt and Pepper to taste

Cook meat and add to other ingredients. Simmer together at low temperature for about 30 minutes. Serve Hamburger over buns