Club soda

Club soda is carbonated water with a small amount of mineral salts added — typically sodium bicarbonate, sodium chloride, potassium sulfate and a little potassium bicarbonate — dissolved into the fizz to give it a slightly fuller, faintly saline, rounder taste than plain soda water or seltzer. It is still essentially calorie-free and sugar-free, but that pinch of minerals softens the sharp edge of the carbonation and lends a subtle savoury depth that many bartenders prefer in a mixer. The name is a piece of Victorian branding that has stuck: club soda is really just soda water with a touch of mineral seasoning.