Weird, they usually detect the bitterness right after touching their tongue with coffee.
Could be they were so delirious with thirst, and their tongues so dry, that they couldn't detect the bitterness and simply focused on the fact that it was moisture.
It's most likely that they were delirious from the dehydration and only jumped at the liquid, and didn't notice the taste.
However, these kos had been suffering from extreme dehydration, and thus had lost the fluidity of their paste.Under normal circumstances, in order to expel the poison, yukkuris would experience vomiting or diarrhea....That was black coffee.Uoeeeeeee!
Ogeeeeeee!
Feelsh baaaad!Mishter tum-tum huuuuuuurtsh!Yu...
Yubu...