- Season meat with garlic powder; place in slow cooker sprayed with cooking spray. Add water and 1/2 cup barbecue sauce; cover with lid. Cook on LOW 8 to 10 hours (or on HIGH 4 to 5 hours).
- Transfer meat to cutting board. Discard all but 1/2 cup sauce from slow cooker. Pull meat into shreds with 2 forks. Add to reserved sauce in slow cooker; stir in remaining barbecue sauce.
- Spoon onto bottom halves of buns just before serving; sprinkle with onions. Cover with tops of buns.