As restaurant chains increasingly turn to specialty beverages to attract customers beyond the traditional meal, Sonic Drive-In believes a business model built around drink customization gives it a head start.Marion Campbell, Sonic's vice president of integrated marketing and communications, told FOX Business that the quick-service restaurant industry is still figuring out how to make specialty beverages a bigger part of its business, while Sonic has spent years building customization into its operations."I think that the market is just getting started. And QSR in particular is just figuring ou...