Combine water and vinegar in a slow cooker set to Low.

Rub oil over entire pork shoulder and let rest for 5 minutes.

Mix brown sugar, seasoned salt, black pepper, cumin, cayenne pepper, garlic powder, onion powder, and cinnamon together in a bowl; rub over entire pork shoulder. Place pork shoulder into the slow cooker. Cover and cook on Low for 6 to 8 hours.

Transfer pork shoulder to a work surface and let rest for 10 minutes. Discard cooking liquid from the slow cooker. Place pork back into the slow cooker and shred. Stir in barbecue sauce.