Freshly squeeze the lemon juice and add it to a tall long drink or tumbler glass.
Add 1 ½ oz of the simple syrup and mix well. Fill the glass with ice and top with about 4 oz sparkling water. Taste and if it’s not sweet enough for you, add the remaining ½ oz of simple syrup.
Garnish with a slice of lemon and a sprig of mint, if you like. Serve immediately and enjoy as an aperitivo with salty snacks.