Download Shake Shack‘s app and get a free ShackBurger (value $5.55), create an account and then order online. You will receive a credit of $5.55 on your order, the price of a single Shackburger. Be certain to use this code: “shackhappy” when you order. You can download the app here: Shake Shack app
Offer expires 2/28/17. Only at participating Shake Shacks that that accept mobile orders. No minimum purchase necessary.