Dunkin’ Donuts: Free Medium Coffee Coupon By Mail December 12, 2009 at 10:03 am By coupongeek How about some FREE coffee? Sign-up for Dunkin Perks HERE and use code DDPERKSCoffee. You’ll then get a coupon in the mail for a FREE Medium Coffee. Thanks, Mama Cheaps! I better go grab one of these for my hubby!