Heat a large skillet or frying pan over medium-high heat.
Add the ground beef to the skillet and cook until browned, breaking it apart with a spatula as it cooks. Drain any excess fat if necessary.
Add the chopped onion, bell pepper, and minced garlic to the skillet with the cooked ground beef. Cook for another 3-4 minutes, until the vegetables are softened.
Stir in the ketchup, brown sugar, Worcestershire sauce, mustard, and chili powder. Season with salt and pepper to taste.
Reduce the heat to medium-low and let the mixture simmer for about 10-15 minutes, stirring occasionally, until the flavors are well combined and the mixture has thickened slightly.
Taste and adjust seasoning if necessary.
Once the Sloppy Joe mixture is ready, toast the hamburger buns lightly if desired.
Spoon the Sloppy Joe mixture onto the bottom halves of the hamburger buns, then cover with the top halves.
Serve hot and enjoy!