In a medium saucepan, add root beer, fish sauce, garlic, and pepper.
Place pan over medium high heat. Bring to a boil. Reduce the heat to low. Simmer until the liquid has been reduced by about 1/2.
Remove the reduction from the heat. Stir in the water.
Allow the sauce to rest until it cools to room temperature.
Place the ribs in a roasting pan. Pour the marinade over the ribs. Cover.
Place pan in refrigerator to chill overnight - or for at least 4 hours.
When ready to cook - preheat the oven to 325°F.
Remove the ribs from the marinade, allowing excess to drip off. Discard marinade. It has touched raw meat and is unsafe to use again.
Place ribs on a baking sheet. Cover the ribs with foil.
Place in preheated oven. Bake for 2 hours, or until the meat is tender but not falling off the bone.
Finish ribs on the grill, by grilling directly over high heat until the outside has caramelized, about 4 minutes on each side.
OR
Switch oven to broil. Broil until side has caramelized. Then flip ribs and broil until other side has caramelized.
Serve hot.