Just for today 8/19 Sonic has medium Slushes for only $0.79

(here is another way to save when going out and in the mood for something sweet and refreshing) 

sonic 8-19-15

You can read more about this deal here
*Please mention when ordering. Limit 4. Tax not included. Excludes Real Ice Cream Slushes. Add-ins cost extra. Cannot be combined with other offers, including Happy Hour. Offer valid only on 8/19/15.