Place the pork tenderloin in a slow cooker; pour the root beer over the meat. Cover and cook on low until well cooked and the pork shreds easily, 6 to 7 hours. Drain well. Stir in barbecue sauce. .
To Freeze: Freeze in freezer safe container
To Reheat: Defrost. Reheat in the microwave or on the stovetop. Serve over hamburger buns.