To take advantage of the deal, you'll need to download the chain's mobile app (if you haven't already) and make sure push notifications are enabled as that's how they'll send the free club sandwich promo code. When you have the code, you just need to start an order on the app and add a 32-oz drink and a McAlister's Club to your order. Then, at checkout, enter the promo code to get the sandwich for free.
Photo via McAlister's Deli.