Mix the sauce: In a bowl, whisk together BBQ sauce, chicken broth, brown sugar, apple cider vinegar, smoked paprika, garlic powder, onion powder, chili powder, and a pinch of salt and pepper.
Add chicken to the crockpot: Place chicken breasts (or thighs) in a single layer.
Pour the sauce over the top, making sure the chicken is coated.
Cook low and slow: Cover and cook on Low for 4–6 hours or High for 2.5–3.5 hours. Chicken should be tender and easily pull apart with a fork.
Shred the chicken: Transfer chicken to a plate and shred with two forks. If there’s excess liquid in the crock, you can ladle some out or let it simmer for a few minutes with the lid off.
Finish the sauce: Stir the shredded chicken back into the crockpot.
Add the butter if using and mix until glossy and saucy. Taste and adjust seasoning—add more BBQ sauce, a splash of vinegar, or a pinch of salt if needed.
Serve your way: Load onto toasted buns with coleslaw, spoon over rice, or tuck into tortillas. Garnish with sliced pickles, green onions, or jalapeños.