Brown the ground beef with the onion and green pepper until cooked through.
Add garlic powder, mustard, ketchup, brown sugar, and pepper; stir and simmer for 10 minutes.
Serve on hamburger buns.
Notes
If you are implementing planned leftovers, try using the leftovers on Sloppy Joe Pizza. Using bulk cooked ground beef from the freezer makes prep for these Sloppy Joes even quicker.