This National Coffee Day, the brand raises not one but two cups in salute of all those who run on Dunkin’ coffee, with a special buy one, get one offer for guests. On Sunday, September 29, anyone who purchases a Hot Coffee at participating Dunkin’ restaurants nationwide will get one Hot Coffee free (of equal or lesser value*). With a second cup on Dunkin’, the brand is making it easier than ever to herald the holiday by recharging and reconnecting with the favorite coffee drinkers in your life.