It is called in Japan, and boricha (보리차) in Korean. While roasted barley tea is generally regarded as a cooling summer beverage in Japan, it is served year-round, hot in winter and cold in summer, in Korea.
Consuming non-fermented barley-based beverages is an ancient practice spanning across the globe; barley water is a popular traditional soft drink in Britain and a similar drink, aguas frescas is frequently sold by street vendors in Mexico.
Originally, roasted barley seeds were stewed in hot water (this is still the method generally used in Korea) but tea bags containing ground barley became more popular during the early 1980s and this is now the norm in Japan. It can be brewed in hot or cold water. Mugicha is usually served cold, but it can also be served hot; the hot version is more popular in the winter. It can also be found from many different distributors in vending machines all over Japan.
According to Japanese food conglomerate Kagome, a recent study stated that drinking mugicha increased blood fluidity. This action is caused by an alkylpyrazine, which is a primary flavor in the drink. Japanese consider it to cleanse the blood of impurities. Mugicha also has been linked with reduced stress during a study by the Institute of Traditional Chinese Medicine and Natural Products in China.
In Korea, roasted unhulled barley is also used to prepare a tea called boricha. More often, it is combined with oksusu cha (roasted corn infusion), as the corn's sweetness offsets the slightly bitter flavor of the barley. A similar drink, made from roasted brown rice, is called hyeonmi cha.