Lay the chicken breasts flat in the bottom of your slow cooker in a single, even layer.
In a bowl, whisk together the BBQ sauce, brown sugar, apple cider vinegar, Worcestershire sauce, garlic powder, onion powder, smoked paprika, black pepper, and salt until fully combined.
Pour the sauce over the chicken, making sure each piece is well coated. Place the lid on top.
Cook on LOW for 5–6 hours or HIGH for 2½–3 hours, until the chicken reaches an internal temperature of 165°F (74°C) and shreds easily.
Remove the chicken from the slow cooker and shred using two forks.
Return the shredded chicken to the slow cooker and stir it into the sauce until every piece is coated.
Serve warm on buns, over rice, in tacos, on baked potatoes, or with your favorite sides.