Cook the Beef:
Heat a large skillet over medium heat. Add the ground beef and cook until browned, breaking it apart with a spatula. Drain any excess grease if needed.
Add the Vegetables:
Stir in the chopped onion, green bell pepper (if using), and garlic. Cook for 3–4 minutes, or until the vegetables soften.
Make the Sauce:
In a small bowl, mix together the ketchup, tomato paste, mustard, Worcestershire sauce, brown sugar, smoked paprika, and water or broth.
Combine and Simmer:
Pour the sauce into the skillet with the beef mixture. Stir to combine.
Reduce the heat to low and let the mixture simmer for 8–10 minutes, stirring occasionally, until the sauce thickens. Adjust seasoning with salt and pepper.
Assemble the Sloppy Joes:
Spoon the beef mixture onto the toasted buns. Serve warm and enjoy!