The battle with Thirst

In Episode 2, Kenstar discovers a bucket of water in the Burning Man's Dojo. Yusuke explains that Kenstar is a fool, saying that they are not defeating thirst, however Kotomaru reveals that he is defeating thirst. Kotomaru is then seen drinking Suntory C.C Lemon, which contains 70 lemon's worth of Vitamin C in every bottle.

It can be assumed that Kotomaru defeated thirst from drinking the lemon drink, but this is never truly revealed.