Place the chicken breasts in the slow cooker. Add the BBQ sauce, liquid smoke, garlic powder, onion powder, and black pepper. Stir to coat the chicken evenly.
Cover and cook on low for 6 to 7 hours until the chicken shreds easily with two forks.
Shred the chicken directly in the slow cooker and stir it into the sauce to absorb the flavors.
In a mixing bowl, combine the coleslaw mix, mayonnaise, apple cider vinegar, and sugar. Toss until the mix is lightly coated.
Spoon the pulled chicken onto the hamburger buns and top each sandwich with a scoop of coleslaw.