At Burger King, get a 4-piece order of Ghost Pepper Chicken Fries for FREE! This deal can be found on the Burger King app and website, and it is good with a $1 purchase. For a brief period only at participating U.S. Burger King restaurants can only be ordered in advance through the BK App and bk.com. Account with Royal Perks is needed. Prior to placing an order, the offer must be activated via the "Offers" option on the BK App or bk.com.