My cat loves to drink from the bathroom sink too. Someone told me that they're programmed to prefer running water to still water because in the wild running water is fresh but still water is most likely stagnant. I've seen those expensive pet drinking fountains and was considering getting one for my cat. Thankfully another fried loaned me theirs and my cat didn't touch it for the whole month. She'd much rather drink out of the sink, or now lick the bottom of the shower or drink from a container of water placed in the shower.

She's weird.