Finely chop the onion and dice the green pepper.
In a bowl, combine Worcestershire sauce, mustard, brown sugar, and tomato sauce.
Heat olive oil in a large skillet over medium/high heat. Add ground beef and cook for about 5 minutes until browned, breaking it up with a spatula.
Season beef with salt and pepper, then add diced peppers and onion. Cook for another 5 minutes until vegetables are tender.
Add minced garlic and sauté for 30 seconds until fragrant. Pour in the sauce mixture and bring to a light boil.
Reduce heat to low and simmer uncovered for 10-15 minutes until thickened, stirring occasionally. Adjust seasoning and add water if desired for a looser consistency.
Serve the Sloppy Joe filling on toasted hamburger buns.