This sentence is saying that the cats in question do not drink any water at all. If this sentence used "l'acqua" it would imply that the cats drink some other water (Think having a specific dish that they don't drink from that the water is contained in, but would drink from some other dish)
doesn't really help me because my understanding was that "bevono l'acqua" is very often translated as "they drink water"...as a matter of fact, here at duolingo if my memory serves me correctly, I have gotten several questions wrong by not including some form of article(l', il, etc.) even when the translation they are asking for in English includes no article
Well in that case, they are most likely dead.
Or maybe just drunk 24/7 with very unhealthy blood alcohol levels. dear lord imagine cats constantly drinking vodka and living
Oh yeah also, Duo talks about cats a lot. I'm getting flashbacks to when it said "I am yours" Duo are you lonely?