Water that has been highly charged with carbon dioxide, which gives it effervescence. Soda water, also called club soda, seltzer water or just plain carbonated water, contains a small amount of sodium bicarbonate, which, because it’s alkaline, can help neutralize an acidic stomach. Soda water is combined with sweeteners and various flavorings to produce a wide variety of soft drinks. Many cocktails also use soda water as an ingredient. See also seltzer water.