Set a slow cooker to Low. Combine water and vinegar together in the slow cooker.
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.
Cook on Low, 6 to 8 hours.
Transfer pork shoulder to a work surface and let rest for 10 minutes. Discard cooking liquid from slow cooker. Place pork back into the slow cooker and shred; add barbeque sauce and stir.