Preheat the oven to 400 degrees F (200 degrees C).

Combine tomato sauce, barbeque sauce, and sugar in a small saucepan. Heat just until sugar dissolves, about 5 minutes. Remove from heat; let cool. Set aside 1/2 cup of the sauce.

Combine beef, pork, flour, onion powder, garlic powder, salt, and pepper in a large bowl. Add the larger amount of tomato sauce and mix until thoroughly combined. Pat meatloaf mixture into a loaf pan; cover with aluminum foil.

Bake in the preheated oven for 30 minutes. Uncover and drain off grease. Slice into serving-sized pieces and pour reserved sauce on top. Bake, uncovered, until no longer pink in the center, 30 to 45 minutes more.