Cucumber-Lemonade Mocktail

Press the cucumber slice against the inside of a chilled highball glass and add ice. In a cocktail shaker, muddle the chopped dill, agave syrup, lemon and lime juices and 1 tablespoon of water until the syrup is dissolved. Add ice, then add the cucumber juice and shake well. Strain into the prepared glass and stir in the club soda. Garnish with the dill sprig.