Buy One ShackBurger, Get One Free at Shake Shack Through January 2, 2022

Shake Shack closes out 2021 by offering a buy-one-get-one-free deal on their signature ShackBurgers through January 2, 2022 when you order online through their website or app at participating locations chain-wide.

To take advantage of the one-time-use offer, you'll need to add two ShackBurgers to your cart and enter the code "THANKYOU21" during checkout. You can save up to $6.39 using the deal (a Shackburger goes for $6.29 in my area).

Shack Shack's ShackBurger is a cheeseburger (an Angus beef patty and American cheese on a potato bun) with lettuce, tomato, and ShackSauce.

Photo via Shake Shack.