Smashburger Coupon for Buy One Entree Get One Free 3 years ago 2 Comments Coupons, Restaurant Deals Smashburger has a great offer right now. Buy one Eentree get another one free with this printable coupon. Offer valid through 3/31/13. Find the Smashburger closest to you here. Prev Article Next Article Sandy P Thanks for the coupon, I have never tried this place… a must for this weekend!! Lindsay Ackerman Guess they need to update their restaurant finder; there are at least 3 in my city and the ZIP code search is telling me my closest is St. Louis.