Whisk salt, black pepper, paprika, and garlic powder together in a small bowl until seasoning is well-mixed. Rub seasoning mixture onto pork loin to coat completely; place loin in a slow cooker.
Whisk cola and ketchup together in a bowl; stir in liquid smoke. Pour cola mixture over pork.
Cook on Low for 6 to 7 hours (or cook on High for 3 to 4 hours). Shred pork using two forks; serve pulled pork on Portuguese rolls.
