Add blueberries and mint leaves to the shaker. Muddle gently to release the flavors.
Pour in the lime juice, rum, and sugar-free simple syrup. Fill the shaker with ice.
Shake for 10-15 seconds until well chilled. Strain into a Collins glass filled with fresh ice.
Top with club soda and stir gently with a bar spoon.
Garnish with fresh blueberries and a mint sprig.
Notes
Fresh blueberries work best, but frozen can be used in a pinch.Store sugar-free simple syrup in the fridge for up to 2 weeks.For extra flavor, let the muddled mixture sit for 2-3 minutes before adding other ingredients.Each drink contains about 120 calories, compared to 220 in a regular mojito.