This deal has ended.
In celebration of St. Patricks Day, Sonic has blasts (milkshakes) for half price all day long today. All you need to do is use the promo code BLAST and order online or in the app. There are a limit of five (5), and add-ins cost extra. Valid on March 17th only. Valid for in-restaurant ordering as well. If you would like to use in-restaurant, please mention the promo code.