"It's mainly for men who are exhausted by the summer's heat," Hayashi said of the beverage, believed to be the first mass-produced eel drink in Japan.
Many Japanese believe eating eel boosts stamina in hot weather.
The fizzy, yellow-colored drink contains extracts from the head and bones of eel and five vitamins -- A, B1, B2, D and E -- contained in the fish.
The Japanese particularly like to eat eel on traditional eel days, which fall on July 24 and Aug. 5 this year.
Demand for eel is so high that Japan has been hit by scores of eel fraud cases, including a recent high-profile incident in which a government ministry publicly scolded two companies for mislabeling eel imported from China as being domestically grown.
The eel involved in recent scandals was prepared in a popular "kaba-yaki" style, in which it is broiled and covered with a sweet sauce. The $1.30 drink costs about one-tenth as much as broiled eel, but has a similar flavor.
Eel extract is also used in cookies and pies made in Japan's biggest eel producing town, Hamamatsu.
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