Sonic 1/2 Price Shakes SaturdayYou’ll love the current Hot Deals, sorry you missed this deal. Shake off the winter blahs and treat yourself to a 1/2 Price Shake All Day at Sonic on Saturday, December 21. This would be a great time to try the holiday shakes, Holiday Mint Vanilla or Chocolate Shake. Check with your local SONIC Drive-In for participation.