In a serving glass, combine lime juice, gin, mint syrup and sparkling water. Garnish with sliced cucumber and sliced lime. Top glass with ice. Add additional mint syrup, according to taste if desired. Serve immediately.
*Mint syrup:Bring to a boil 1 cup water, 1 cup sugar, and a handful of torn mint leaves. Remove from heat, cover pot, and allow mint to steep for 30 minutes. Strain mint and store mint syrup in the fridge until ready to use.