SONIC® Drive-In introduces ice cream's smoother, creamier cousin — the new Custard Concretes America's Drive-In Expands Menu with New Platform of Frozen Treats OKLAHOMA CITY, 2017-Apr-25 — /EPR Retail News/ — SONIC® Drive-In (NASDAQ:SONC) introduces new Custard Concretes; ice cream's smoother, creamier cousin. In one bite, the rich frozen Custard Concretes provide high-quality flavor found only at SONIC. New…