In small bowl, whisk together ketchup, apple cider vinegar, onion, garlic, chili powder and hot pepper sauce.
Place chicken breasts in glass baking dish. Pour sauce over chicken, turning to coat all sides. Turn chicken skin-side up. Place in oven and bake 1 hour. Set aside until cool enough to handle.
While chicken is cooling, in large bowl, stir together cabbage, mayonnaise, yellow mustard, apple cider vinegar, celery seeds, salt and pepper. Set aside.
Discard chicken skin. Pull meat off bones; place meat in saucepan. Scrape sauce out of baking dish and stir into saucepan. Over low heat, warm chicken until hot throughout. Open buns on plates; top with chicken and slaw. Close buns and serve.