Shake the gin, lemon juice, and syrup and strain into a highball glass (but see note) with ice. Fill with club soda. No garnish.
A fizz, or Delmonico, glass is a highball-style glass but just a little shorter, with an 8- to 10-ounce capacity. Since the fizz-type drinks containing egg are served without ice, this glass is preferable to the standard highball.