Restaurant Deals Sonic | 79¢ Medium Slushes August 19, 2015 Wendy Sonic 79¢ Medium Slushes from Sonic today, 8/19! *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.