OKLAHOMA CITY, 2016-Sep-28 — /EPR Retail News/ — Sonic Corp. (NASDAQ:SONC), the nation's largest chain of drive-in restaurants, today (Sep 27, 2016) announced preliminary results for its fourth fiscal quarter ended August 31, 2016. The company estimates that system-wide same-store sales for its fourth fiscal quarter decreased approximately 2.0%. Estimated same-store sales performance reflects a decrease of…