Frontera's Sparkling Limeade

We got this at the Frontera sandwich shop in O'Hare airport. All three of us loved it and it has been in the back of my mind ever since.

1/2 to 2/3 cup sugar
1 1/3 cups freshly squeezed lime juice (roughly 8 to 10 limes)
1 quart sparkling water

Add the smaller amount of the sugar to the lime juice in a pitcher and stir until the sugar is dissolved. Add the sparkling water, stir and taste for sweetness; add more sugar if desired. Pour over ice and serve immediately.

Credit: Authentic Mexican by Rick Bayless