makes as many as you want

Selter or sparkling water

Nellie & Joe's Key West Lime Juice

Simple syrup

This is really a no-recipe drink. It's mostly seltzer with a splash of key lime juice and simple syrup—the amount depend on your tastebuds. If you're serving it at a party, I suggest making a large batch and refrigerating it a few hours before so you can just pour and serve as needed.