Mix the clementine juice and cranberry juice in a large pitcher.
Add the simple syrup and stir until well combined.
Fill tall glasses with ice cubes.
Pour the juice mixture until glasses are 2/3 full.
Top each glass with sparkling water. Then, gently stir to combine.
Garnish with fresh cranberries, clementine slices, and mint sprigs if desired.
Notes
Make the drink base up to 24 hours ahead and add sparkling water just before serving.For a sweeter drink, adjust the simple syrup amount to taste.Replace regular ice cubes with frozen cranberries to prevent dilution.Store any leftover juice mixture in an airtight container in the fridge for up to 3 days.This recipe makes 6 servings and can be doubled for larger gatherings.