Carbonated water (also known as club soda, soda water, sparkling water, seltzer water, or fizzy water) is water into which carbon dioxide gas under pressure has been dissolved. Some of these have additives such as sodium (seltzer water is almost always composed of water and carbon dioxide with no other additives). This process, known as carbonation, is a process that causes the water to become effervescent. Most carbonated water is sold in ready to drink bottles as mineral water and carbonated beverages such as soft drinks. However, it is rather easy to prepare at home with soda makers.