Preheat oven to 425℉. Lightly grease a 9x13 baking dish with cooking spray. Set aside.
In a large skillet, heat olive oil over medium heat. Add green pepper and onions and saute for 6-8 minutes, or until softened.
Add ground beef to skillet, along with garlic powder, onion powder, salt, and pepper. Cook and crumble beef until no longer pink. Drain grease, if needed.
Add sugar, vinegar, ketchup, barbecue sauce, and mustard to skillet. Stir well to combine, then bring mixture to a boil, reduce heat, and simmer on low for 4-5 minutes. *If you feel the mixture needs to be more saucy, add a few more tablespoons of ketchup and/or barbecue sauce.*
Spoon beef mixture into prepared baking dish. Sprinkle one cup of shredded cheese evenly over mixture. Place tater tots in an even, single layer on top of cheese. Then top with remaining cheese.
Bake for 25-28 minute, or until tots are cooked through and golden brown. Remove from oven and let cool for 5 minutes, then serve.