One of the shakes is a Brownie Batter Shake which includes a hand-mixed combo of vanilla ice cream and chocolate brownie batter. The second one is the return of Sonic's Yellow Cake Batter Shake which is a hand-mixed shake with vanilla ice cream and yellow cake batter.
The company wanted to create these ice cream products to capture the fun and thrill of "baking with the family into two creamy, sippable versions every dessert lover will find irresistible." The cake shakes are only available for a limited time. They're there now and you'll find them until August 2nd.