Season the chicken breasts with salt and black pepper on both sides.
In a medium bowl, combine the barbecue sauce, apple cider vinegar, honey, Dijon mustard, smoked paprika, garlic powder, onion powder, and crushed red pepper flakes. Mix well to create the zesty barbecue sauce.
Place the seasoned chicken breasts in the slow cooker.
Pour the zesty barbecue sauce evenly over the chicken breasts.
Cover and cook on low for 4 hours, or until the chicken is tender and cooked through (internal temperature should reach 165°F or 74°C).
Once cooked, remove the chicken breasts and shred them using two forks.
Return the shredded chicken to the slow cooker and stir to coat with the sauce.
Serve the zesty barbecue chicken garnished with chopped fresh cilantro.