Special equipment: a slow cooker
In a 4- to 6-quart slow cooker, combine the ground beef, garlic, celery, peppers, onions, tomato sauce, ketchup, chili powder, dry mustard, onion powder, sugar, Worcestershire sauce, 1 teaspoon salt and 1/4 teaspoon pepper. Mix together with a wooden spoon, making sure to break up the ground beef. Set the machine to high and cook for 4 hours.
Spoon the sloppy joe mixture onto the buns to make sliders.