A classic mocktail if there ever was one. The lime and mint are still there even if the booze is not, and those are the classic flavors you are probably looking for in this mocktail anyway.
Build it in the glass and go easy on the sugar for starters. And always use fresh mint. No shortcuts with this one.
Cheers!
6 fresh mint sprigs (plus 1 for garnish)
1 barspoon superfine sugar
2 lime wedges
Soda Water
Dash of simple syrup
Muddle the mint, sugar and lime in a highball filled with ice
Top with Soda Water and muddle gently
Add simple syrup to taste (start with the barspoon you used with the sugar)
Garnish with mint sprig
Source: Mocktails: cordials, syrups, infusions and more book