The cult canned iced tea and vodka beverage, led by Clement Pappas and Matt Quigley, could bring in $300 million this year—in the golden age of ready-to-drink cocktails.

While it does seem like every day from May through October should be National Ice Cream Day, that isn’t actually the case. No, that day this year is Sunday, July 20. So, how can you celebrate? Simple: ...