Since eel is supposed to give you an energy boost, the Japanese encourage eating lots of it during the summer to combat natsubate, or heat lethargy. In fact, there's even a specific day called Doyo Ushi no Hi during late-July, when temperatures are at their hottest, dedicated to eating unagi, or grilled eels.
So leave it to the country who bats nary an eyelash at strange flavor combinations to come up with eel soda. Called Unagi Nobori (which translates to "Surging Eel"), the beverage contains eel extract and vitamins commonly found in eel. Yellow in color, the carbonated drink apparently has a similar taste to unagi. It's like an energy drink and liquid meal hybrid!