The Tom Collins never tasted the same after the invention of sour mix. But there's no reason to take this supposed shortcut; mixing the drink from scratch is really very simple. Classic Cocktail Recipes
Pour the lemon juice into a collins glass. Add the superfine sugar and stir briskly to dissolve. Fill the glass with ice and add the gin. Top off the glass with club soda and stir. Garnish with a lemon slice.