Heat a large nonstick skillet over medium heat.
Cut the chicken into bite-size pieces. Spray the skillet with olive oil spray and add the chicken breast. Season with garlic powder, onion powder, salt, and pepper. Cook until the chicken is slightly pink then push to the side.
Add the sliced red onion to the other side of the pan. Cook until the onions are soft, then remove them from the pan.
Pour the BBQ sauce on the chicken and stir together. Let it cook for another minute so the BBQ sauce is heated through.
Add half of the chicken to the bottom of a sub bun. Top with onions, then one slice of cheese. Repeat with the second sub.
Place under the broiler until the cheese melts, it should only take 1-2 minutes.