Preheat the oven to 400°, and spray a 13x9-inch baking dish with cooking spray.
In a large skillet, cook the beef, onion and garlic over medium high heat till the beef is no browned, about 10 minutes.
Drain any grease and add the bell pepper, tomato sauce, tomato paste, ketchup, BBQ sauce, brown sugar, yellow mustard, Worcestershire sauce, and vinegar. Cook for 5 minutes.
Place half the tater tots in the bottom of the baking dish. Pour the sloppy joe mixture over the tater tots, then sprinkle with half the cheese.
Top with the remaining tater tots.
Place the pan in the oven and bake for 35 - 40 minutes, till the casserole is bubbly and the potatoes get browned and crispy.
Remove and add the remaining cheese and place back in the oven for 5 minutes.