Place mint leaves in the pitcher. Press gently with a muddler to release the oils.
Add mango cubes to a blender. Blend until smooth, about 30-45 seconds.
Pour the mango puree into the pitcher with the muddled mint.
Add lime juice and simple syrup. Stir to combine.
Pour in cold water and stir well.
Add club soda just before serving.
Fill glasses with ice cubes.
Pour the mocktail mixture into glasses.
Garnish each glass with mint sprigs and lime slices.
Notes
Store the base mixture without club soda in the fridge for up to 24 hours.Add club soda right before serving to keep the drink fizzy.For extra sweetness, adjust simple syrup to taste.Strain the mixture if you prefer a smoother texture without mint leaves.Choose mangoes that yield slightly to pressure for the best flavor.