Summer just got sweeter.Credit: Allrecipes / SonicAs a self-proclaimed sucker for soda, I can affirm that nothing hits quite like a crispy Diet Coke with extra ice from the drive-thru. But beyond your standard Coca-Cola and Pepsi offerings, fast food chains have been stepping it up with a variety of exclusive drinks to keep fizzy fans on their toes, from dirty soda to Refreshers.Coffee chains, such as Dunkin' and Starbucks, have had Refreshers f…