Same-Store Sales Growth for the Fourth Fiscal Quarter 2015 Was 4.9% Fourth Fiscal Quarter 2015 Earnings Conference Call Date Announced OKLAHOMA CITY, 2015-9-16 — /EPR Retail News/ — Sonic Corp. (NASDAQ:SONC), the nation's largest chain of drive-in restaurants, today announced system-wide same-store sales for its fiscal 2015 of 7.3%. Same-store sales growth reflected an increase of approximately…