Many dogs, and not a few cats are toilet water connoisseurs. I believe there is a cooling effect.
Water is well known for that property.
Dogs are well-known for their propensity to eat their own (and others') feces and vomit. Cats will happily clean their anuses with their tongues. Perhaps this all adds to their willingness to consume toilet water, or perhaps even creates in them a kind of desire for it, given the scatological and urological properties it most likely contains.
This is far too much analysis for a Monday morning. lol
There's no goin' back now!