FREE Whopper for National Burger Day at Burger King Posted On June 2, 2020 Get a FREE Whopper for National Burger Day at Burger King! Go to your Burger King App and scroll down to offers until you see “National Burger Day” to enter code “LUCKYWHOPPER” for your free Whopper, there’s no purchase necessary. Close the App and refresh your offers, you should see the offer to redeem. Expires 6/2/2020.