Enroll in the Dunkin Donuts Perks program and use promotion code: DDPERKSCoffee. You’ll get a free medium drink just for joining and another free drink coupon mailed to you during your birthday month! Free medium beverage of choice includes any iced or hot coffee, tea or latte, hot chocolate or Coolatta. NOTE:You need a DD card to enroll. You can get one in-store, online or by downloading their mobile app.