Phew! Thank goodness this sign was there above the toilet! I was this close to dipping my cup in.
As goofy as this sign is, it's actually in reference to something pretty cool. It is from the bathroom at the Hollywood Beach in Chicago, which I visited yesterday. This other sign in the bathroom explains the "cool" part a bit better though:
The building collects rain water through the roof and the permeable pavement around the bathroom. The water gets filtered (not enough to drink it, apparently), then stored and pumped into the toilets for flushing. They say it saves 30,000 flushes worth of water every year!