Mugi-Cha Tea is not a tea proper, but a Japanese tisane made from roasted barley.
It can be drunk cold during the summer, especially with ice.
It is sold in large, very long tea bags that resemble really long, old-fashioned tampons. You are supposed to put them into empty, really large plastic pop bottles (called PET bottles by the industry), and brew the iced barley tea up in that.
Some of the tea bags of Mugi-Cha sold can be “brewed” with cold water, saving you having to boil it up, then chill it.
Mugi-Cha Tea is popular in Korea as well.