In a large skillet over medium heat, cook the ground beef until browned, breaking it apart as it cooks.
Drain any excess grease from the skillet.
Add the diced onion and minced garlic to the pan.
Cook for 2-3 minutes, stirring often, until the onions are soft and fragrant.
Stir in the tomato sauce, ketchup, brown sugar, Worcestershire sauce, mustard, salt, black pepper, and smoked paprika.
Mix well until all ingredients are fully combined.
Pour in ½ cup of water and stir to incorporate.
Lower the heat and let the mixture simmer for 10-15 minutes, stirring occasionally, until the sauce thickens.
While the sloppy joe mixture simmers, lightly toast the hamburger buns in a skillet or oven if desired.
Spoon the sloppy joe mixture onto buns and serve immediately.