Keyboards are very cheap, you can easily buy them. Make sure you buy the correct one, Swiss / French / German / UK etc http://www.amazon.co.uk/s/ref=sr_hi_...puter+keyboard
Or, look around the computer scrap places at your local dump.
Or switch off & unplug the keyboard. Find a diagram of your
keyboard key positions (Qwerty, Quertz etc) http://en.wikipedia.org/wiki/Keyboard_layout
& then remove the keys, by popping them up with 2 flat head screwdrivers.
Now you should be able to wash the plastic parts with a damp (Not wet) rag. Do this with the keyboard upside down, so there is no chance of the water running into the switches. Leave the keyboard and keys to dry upside down overnight and next day replace the keys in the correct places.
We used to take all the keys off, put them in a muslin bag, and wash them thoroughly, dry them, and replace them the next day.