Friday, September 18th, is National Cheeseburger Day! teak ‘n Shake is offering all loyalty app members $2 off (aka 50% off) the Double ‘n Cheese Steakburger from September 18th through September 24th. Limited to one per order, per visit. The offer will only be valid on orders placed through the app. This might be a good time to join the Steak ‘n Shake Rewards Club. Download the Rewards Club app and receive a FREE Specialty Milkshake with your first purchase as a club member. A Double ‘n Cheese Steakburger and a Specialty Milkshake – what better to celebrate National Cheeseburger Day?