Wow this is a thrifty deal! Now through June 27th when you order a Real Ice Cream Shake at Sonic you can get a second shake free or get a coupon for a free shake for next time you visit! Simply order your shake(or malt or cream pie shake) and get the second free, no coupon required! Otherwise, if you just order one shake make sure you get your free coupon for your next visit!
Find more details HERE.