Sign up for the Dunkin Perks an you'll:
Earn $1 Dunkin' Dollar for every $20 you spend in a calendar month
Earn $2 Dunkin' Dollars for every $20 you spend on your DD Card if your Card Auto-Recharges once within the calendar month.
and get a coupon for a free medium bevarage of your choice and another one on your birthday.
Click on little photo that say's "FREE medium beverage".