Soda water

Soda water is plain water made fizzy by dissolving carbon dioxide under pressure — the simplest of all carbonated drinks and, in its unflavoured form, essentially calorie-free. Clear, sharply bubbly and faintly tart from the carbonic acid the gas forms in the water, it carries no sugar, no sweetener and no flavour of its own, which is exactly why bartenders reach for it: it lengthens and lifts a drink without adding anything but sparkle. In everyday speech "soda water," "seltzer" and "club soda" are used almost interchangeably, though club soda usually carries a pinch of added mineral salts that soda water and plain seltzer do not.