- Carbonated water, also known as sparkling water, fizzy water, soda water, club soda, or seltzer water, is plain water into which carbon dioxide gas has been dissolved. The process of dissolving carbon dioxide gas is called carbonation.
Club soda may be identical to plain carbonated water or it may contain a small amount of table salt, sodium citrate, sodium bicarbonate, potassium bicarbonate, potassium sulfate, or disodium phosphate, depending on the bottler. These additives are included to emulate the slightly salty taste of homemade soda water. In the UK Soda Water is nearly always made with Sodium Bicarbonate.