For the simple syrup-
Combine the water sugar, water, and basil in a small saucepan. Over medium heat simmer until the sugar is dissolved. Remove the basil leaves and cool completely.
In a large container combine the orange, lemon, and lime juice.
Add the sparkling water.
Add the infused simple syrup one tablespoon at a time, tasting as you go, until you have the right sweetness and flavor.