Heat a large skillet over medium-high heat. Add the ground beef, diced yellow onion, and diced green bell pepper, then cook for 6–8 minutes while breaking up the beef until it is browned and the vegetables begin to soften.

Drain excess fat if necessary, especially if the beef leaves a noticeable amount of grease in the skillet. Lean 85–90% ground beef generally needs little draining, but removing excess fat keeps the finished sauce rich rather than oily.

Add the minced garlic and cook for about 30 seconds, stirring constantly. This brief cooking time releases the garlic’s savory aroma without allowing it to burn.

Stir in the ketchup, water, packed brown sugar, yellow mustard, Worcestershire sauce, and salt. Scrape the bottom of the skillet as you mix so the sauce coats the beef and vegetables evenly.

Bring the mixture to a gentle simmer, then reduce the heat. Cook uncovered for 5–10 minutes, stirring occasionally, until the filling is thick, glossy, and easy to pile onto buns.

Toast the hamburger buns if desired, then spoon the hot Sloppy Joe mixture onto 4–6 buns. Serve immediately while the filling is warm and saucy.