Stir the barbecue sauce, brown sugar, bourbon, garlic powder, and smoked paprika together in a slow cooker insert.
Season to taste with salt and pepper.
Add chicken breast, and turn to coat in sauce.
Cover and cook on LOW for 4-6 hours.
Let sit in sauce for 15 minutes.
Choose a barbecue sauce that you like. The flavor of the barbecue sauce will change the overall flavor of the chicken. For example, you can use a sauce with a little heat for a spicier sauce or pick a sauce with brown sugar or honey for a sweeter sauce.
Feel free to substitute an equal amount of apple juice for the bourbon.