Restaurant Deals Sonic Drive-In | Half Price Cheeseburgers on July 21 July 19, 2016July 19, 2016 Wendy Sonic Sonic Drive-In Restaurants are offering up 1/2 price single-patty Cheeseburgers all day Thursday, July 21, 2016! NO coupon needed – just mention the deal when ordering. Plus, don’t forget about 1/2 price drinks from 2-4 pm daily!