Lightly grease the slow cooker with cooking spray.
Place the chicken breasts in the bottom of the slow cooker.
In a bowl, whisk together the barbecue sauce, chicken broth, brown sugar, Worcestershire sauce, apple cider vinegar, smoked paprika, garlic powder, onion powder, salt, pepper, and chili powder.
Pour the sauce evenly over the chicken.
Cover and cook on LOW for 5 to 6 hours or HIGH for 2½ to 3 hours.
Remove the chicken and shred it using two forks.
Return the shredded chicken to the slow cooker and stir until fully coated in the barbecue sauce.
Cook for another 15 to 20 minutes on LOW to absorb the sauce.
Garnish with chopped parsley before serving.