Preheat your oven to 350˚.
Heat a large pan/skillet, add in your beef and onions. Brown and break up the beef, once it is done remove it from the pan and drain the excess fat.
In the same pan/skillet add the tomato sauce, brown sugar, brown mustard, apple cider vinegar, Worcestershire sauce, salt and pepper. Bring it to a boil and remove about 1 cup of it.
Add in your water, garlic, rice and ground beef. Mix it all together and allow it to cook for about another minute.
In your baking dish add reserved BBQ sauce and beef broth and mix together, lay your halved peppers in the sauce and scoop the beef and rice mixture into each pepper. Top with shredded cheddar cheese, cover with foil and bake for about 45 minutes.