In UK English at least, the word order feels very odd. "When he is thirsty, he even drinks water" would be better.
Good news... "When he is thirsty, he even drinks water" is among the accepted translations!
The audio for this one, even at slow speed is slightly distorted - "pije i vodu" sounds very much like "pije TY vodu." Granted, "ty" wouldn't make sense, but it would be better if the word sounded like what it is. I have reported it.
What is the difference in usage of "kdy" and "když" if the translation is "when"?