1. Fill a crock pot half way with water. Add onion, vinegar and chicken. Cook on high for 3 - 4 hours or until the chicken is done and comes easily off the bone.
2. Remove chicken from crock pot and shred. Place shredded chicken back in the empty crock pot and add the sauce. Stir to combine sauce with chicken and let cook until heated through. You can let it sit in the crock pot on low for up to 4 - 5 hours before serving.
3. Serve on rolls with cole slaw.