Fill a glass with ice cubes.
Pour in the elderflower syrup and lime juice over the ice.
Add fresh mint leaves to the glass and gently muddle them with a muddler or the back of a spoon to release their flavor.
Slowly pour the sparkling water into the glass, allowing it to mix with the other ingredients.
Garnish with lime slices and fresh berries if desired.
Stir gently and serve immediately with a straw or stirring stick.