01 - In a blender, combine thawed cherries, freshly squeezed lemon juice, and agave syrup. Blend until completely smooth.
02 - Strain the cherry mixture through a fine mesh sieve into a cocktail shaker to remove all pulp.
03 - Add cherry juice to the shaker. Fill with ice and shake vigorously for 15 seconds.
04 - Strain the mixture evenly into two chilled martini glasses.
05 - Gently top each glass with cold sparkling water to retain effervescence.
06 - Garnish each glass with a fresh cherry and, if desired, a twist of lemon zest or a sprig of mint. Serve immediately.