Heat the oil in a skillet over medium heat. Sauté the diced onion until it starts to soften.
Add the minced garlic and chili powder to the skillet, stirring well to combine.
Crumble the lean ground beef into the skillet and cook until it is no longer pink.
Season with salt, black pepper, and brown sugar. Pour in the ketchup, tomato sauce, and water. Stir everything together, ensuring the beef is well-coated in the sauce.
Simmer the mixture for about 10 minutes, allowing the flavors to meld together and the sauce to thicken.
Toast the hamburger buns or slider buns until lightly browned.
Spoon the Sloppy Joe mixture onto the bottom halves of the buns. Top with the remaining bun halves.
Serve hot and enjoy the messy deliciousness of Homemade Sloppy Joes.