SONIC holds annual Unturkey Day on November 21: offers Half-Price Cheeseburgers all day!   SONIC Offers Guests Half-Price Cheeseburgers on November 21 for Annual Unturkey Day OKLAHOMA CITY, 2017-Nov-21 — /EPR Retail News/ — In honor of the upcoming Thanksgiving holiday, SONIC Drive-In Chief Marketing Officer, Lori Abou Habib, is taking a bold stand and pardoning all turkeys on Tuesday, November 21. Known by SONIC fans far…