- Sign in to your Shake Shack account https://shakeshack.com/home#/menu/productDetails/11689/5184241
- For mobile orders, download/install the Shake Shack app
- Click "Order Now"
- Select Pickup or Delivery
- Add quantity of 2 ShackBurgers (Single only) to cart.
- In cart, apply Buy 1, Get 1 Free promo code THANKU2021 or THANKYOU21
- Buy 1, Get 1 Free Discount will be applied.
- Proceed to checkout and complete your order.