Carbonated waters are waters that have been injected with carbon dioxide. It's the carbon dioxide that gives them their "fizzy" or bubbly quality. Yet, the various carbonated waters differ from one another in terms of their ingredients. Beverages labeled "club soda" or "soda water," for example, contain sodium bicarbonate or baking soda. Carbonated waters called "seltzer" and "sparkling water," on the other hand, consist of only water and carbon dioxide. Some carbonated waters also contain sugar while others do not. "Tonic water" contains 2.6 to 2.9 grams of sugar per fluid ounce whereas club soda is sugar-free. Carbonated waters can also contain other kinds of ingredients. Tonic water, for instance, contains quinine, a bitter, colorless substance that is also found in medicines used to treat malaria, while club soda includes mineral salts such as citrate and phosphate.