If using the optional sugar garnish: Using a lime wedge, moisten the rim of two glasses. Sprinkle sugar onto a plate and dip the moistened rim of the glass into the sugar.
Pour the tart cherry juice, lemon juice, lime sparkling water, and agave (if using) in a glass or jar. Mix well.
Add ice to each glass. Pour half of the sparkling lemonade into each.
Top off with another splash of sparkling water or a squeeze of fresh lime, if desired.
*The agave for sweetener is optional. I like really tart flavors and the sugar on the rim of the glass is generally enough sweetness for me. However, 1-2 tbsp of sweetener does balance the flavors well and especially nice if you are not using the sugar on the rim of your glass.
~Nutrition facts calculated for drink with 1 tbsp of agave and no garnish.