Preheat your smoker or grill to 225°F (107°C).
In a bowl, mix brown sugar, smoked paprika, garlic powder, onion powder, salt, and black pepper.
Rub the spice mixture all over the pork belly cubes.
Place the pork belly cubes on the smoker grates.
Smoke the pork belly for about 2 hours.
In a bowl, combine barbecue sauce and apple cider vinegar.
After 2 hours, remove the pork belly and place it into an aluminum pan.
Pour the barbecue sauce mixture over the pork belly.
Cover the pan with aluminum foil and return it to the smoker for another hour.
Uncover and cook for an additional 30 minutes to caramelize the sauce.