Place the chicken breasts in the bottom of the crock pot.
In a medium bowl, whisk together barbecue sauce, chicken broth, apple cider vinegar, brown sugar, smoked paprika, garlic powder, onion powder, salt, and black pepper until well combined.
Pour the sauce mixture evenly over the chicken breasts in the crock pot.
Cover and cook on low for 4 hours, or until the chicken is tender and easily shredded with a fork.
Remove the chicken breasts from the crock pot and place them on a cutting board.
Use two forks to shred the chicken into bite-sized pieces.
Return the shredded chicken to the crock pot and stir to coat it evenly with the sauce.
Let the shredded chicken cook on low for an additional 15 minutes to absorb the flavors.
Toast the sandwich buns if desired.
Scoop the shredded chicken onto the bottom half of each sandwich bun and top with the other half.
Serve immediately and enjoy your crock pot chicken sandwiches.