Think Geek has an innovative product listed on their site…a clock that runs off of water! Actually from their website, it looks like you could use any type of electrolytic fluid such as beer, soda or even coffee.
Think Geek explains how it works:
How does it work? Magic mostly. And a little bit of science too. The internal converter simply extracts electrons from water (or other liquid) molecules and provides a steady stream of electrical current acting as a fuel cell to generate power to the clock.
The cute little digital clock can run off water (or your liquid choice) for many weeks and the creator has even left a small opening to place your flowers. Isn’t it nifty?