Rim a highball or rocks glass with sugar: run a lime wedge around the rim, then press it into fine sugar and set aside.
Fill the glass with ice cubes.
Add 45ml gin, 6ml grenadine, 45ml fresh lime juice, and 6ml simple syrup directly over the ice.
Top with 90ml soda water and stir gently once with a bar spoon to combine without losing carbonation.
Garnish with a lime wheel on the rim.
A cocktail glass is a poor fit for a built, ice-filled sparkling drink - a highball gives the soda water room to breathe and keeps the drink cold longer. Use freshly squeezed lime juice; bottled juice will flatten the citrus brightness that defines this cocktail.
My Bar Shelf reads your shelf and shows you every cocktail you can make from what you already own, including Jitterbug.