Restaurant Deals Sonic Drive-In | Half Price Cheeseburgers tomorrow 7/29 ONLY July 28, 2015 Wendy Sonic Tomorrow only, Sonic Drive-In Restaurants are offering up 1/2 price SONIC® single-patty Cheeseburgers all day! There’s a limit of 5 per customer. NO coupon needed – just mention the deal when ordering. July 29th only.