Pour in vodka, fresh lime juice, and simple syrup.
Blend on high until smooth and slushy.
Add lemon-lime soda (or sparkling water) and pulse briefly to combine without losing bubbles.
Taste and adjust sweetness or tartness if needed.
Pour into chilled glasses and garnish with lime wedges and cherries. Serve immediately.
Notes
Fresh lime juice gives the brightest flavor. For extra cherry punch, add a spoonful of cherry syrup. If too thick, blend in a splash more soda; if too thin, add a handful of ice or more frozen cherries.