FREE Shake at Wayback Burgers!!! This post contains affiliate links which means that we may be compensated if you click a link and make a purchase.. June 11, 2019 by Karen-Kupon Girl Leave a Comment Free Shake at Wayback Burgers Cool off with a free shake at Wayback Burgers! Stop by your local Wayback Burgers on Free Shake Day to get a free 12 oz. Black & White milkshake. No purchase necessary! Valid June 21st only. Have you tried the burgers? Karen – Kupon Girl Get These Freebies: A Grocery Budget List + Pantry Checklist Printable when You Sign up for the Kupon Girl Newsletter"We Respect Your Email Privacy"