Place pork into the slow cooker. Season with salt, pepper, onion powder, and garlic powder. Pour beer into the bottom of the slow cooker. Cover and cook on High for 1 hour. Reduce the heat to Low and cook until meat is tender and can be easily pulled apart with a fork, 8 to 10 hours.

Remove pork from the slow cooker and shred with two forks. Discard cooking juices. Return shredded pork to the slow cooker and stir in barbecue sauce. Cover and cook on Medium for 1 hour.