A variety of different drinks contain either natural or added caffeine. Tea, coffee, and chocolate are all examples of natural sources of caffeine, so drinks made of these substances typically contain the stimulant. Many soft drinks, such as sodas, contain caffeine as an additive, in which case it will usually be listed on the label as an ingredient. These drinks all contain varying amounts of caffeine, and the original source of the stimulant can potentially result in different effects. This is due to the fact that certain polyphenols and other compounds may form complexes with caffeine that are not easily soluble.
Caffeine is a molecule that occurs naturally in plant materials such as coffee beans and tea leaves. Other natural sources include the kola nut, seeds of the guarana plant, and yerba mate leaves. Regardless of the source, caffeine tends to have a stimulating effect on the human nervous system. Some people seek out food and drinks that contain caffeine for this effect, while others choose to abstain.
Coffee and tea are two popular drinks that naturally contain caffeine. Though these drinks are made from different plant products, the caffeine they contain is chemically the same. At one point the caffeine in tea was known as theine, though these compounds were later shown to be the same. Drinks made from yerba matte were originally thought to contain a compound known as mateine, but this was also later found to be caffeine. The physiological effects associated with caffeine from different natural sources may vary not due to them being molecularly different, but because of the presence of other xanthines and insoluble polyphenols.
Cola flavored soft drinks originally contained extract of the kola nut, which is another natural source of caffeine. Artificially flavored soft drinks of this nature still often contain caffeine, though as an additive. Many other soft drinks contain caffeine as well, especially energy drinks. When these drinks contain added caffeine, it will typically be listed as an ingredient so that the presence of the stimulant can easily be determined.
Drinks that naturally contain caffeine can also be obtained in decaffeinated forms. At one point this process used benzene and other solvents to strip the stimulant, though less environmentally damaging methods are now commonly employed. In addition to decaffeinated tea or coffee, this process also results in caffeine extract that can then be added to other drinks or used as a supplement.