沙士(Root Bear)來源不可考，應該是墨西哥原住民用來解熱的自然草本飲品。美國人移民新大陸，且往中美洲擴展勢力範圍後，成為美國民眾常喝飲料。據史載，19世紀，沙士與薑汁水為美國人常喝的兩種解渴飲料。可樂發明人潘博頓（John Pemberton）當初調配具有古柯鹼成分的可樂，其用意之一是為了取代當時盛行於美國的沙士。
it is called root beer here. The soft drink version of root beer is non-alcoholic and is generally made using root beer extract or other flavored syrups along with carbonated water. The soft drink version of root beer constitutes about 3% of the American soft drink market.
The alcoholic version is made from a combination of vanilla, cherry tree bark, licorice root, sarsaparilla root, artificial sassafras root bark flavoring (the natural form is mildly carcinogenic), nutmeg, anise, and molasses among other ingredients.
Many local brands of root beer exist, and homemade root beer is made from concentrate or (rarely) from actual roots. Both alcoholic and non-alcoholic root beers have a thick and foamy head when poured.
 Optional ingredients
Root beer may also include allspice, birch bark, coriander, juniper, ginger, wintergreen, hops, burdock root, dandelion root, spikenard, pipsissewa, guaiacum, yellow dock, honey, clover, cinnamon, licorice, prickly ash bark, quillaia, and yucca. Because of their pleasant flavor and medical properties some of the root beer ingredients have also occasionally been used in other products such as toothpaste, soap and medicine. This could explain why some people tasting root beer for the first time say that it reminds them of these products.
Due to the wide variety of ingredients possible, the flavor of root beer is widely variable between brands.
In Britain, there are several different root beers, which rose to prominence with the temperance movement in the 20th century. These include sarsaparilla, dandelion and burdock, and ginger beer. They were strongly flavored drinks that people could use as an alternative to alcoholic beverages, and there tended to be a strong local preference for one of these. Well into the 1960s, these outsold cola drinks.