1. Season meat with garlic powder; place in slow cooker. Add beer and 1/2 cup barbecue sauce; cover with lid. Cook on LOW 8 to 10 hours (or on HIGH 4 to 5 hours). 2. Meanwhile, mix mustard, sugar and vinegar until blended. Add to coleslaw blend in medium bowl; mix lightly. Refrigerate until ready to serve. 3. Transfer meat to cutting board. Discard all but 1/4 cup sauce from slow cooker. Pull meat into shreds with 2 forks. Add to reserved sauce in slow cooker; stir in remaining barbecue sauce. 4. Fill rolls with meat mixture and 1/4 cup coleslaw.
Note: Substitute beef broth or apple cider for the beer.