No matter how they're initially cooked, ribs have a tendency to dry out in the refrigerator. The best way to reheat them is at a very low temperature, either on a grill/smoker or in the oven. Set the oven or grill to 225°F and reheat for about 30 minutes. To help keep them moist, wrap them in foil and add a small amount of water or extra sauce over the cooked ribs before wrapping them. Also, be sure to bring the meat to room temperature before reheating