There is a lot of information about the Euro banknotes but the most important is: It is perfectly save to wash Euro banknotes in the washing machine*. They get clean and are fit for use next time you go shopping. Alternatively, one could try and remember emptying all jeans pockets before washing.
Washed banknotes: 5, 10, 20 and 50€ (not all at once – this post reflects years of experience)
Washing programme: 30°C, 40°C, Colour and white
La puce, die Welt and everything else 
It is perfectly safe to go kayaking with Euro banknotes, too. Drop them into the Baltic Sea, fish them out again and go dining.
(The waiter took the notes with just two fingers and stored them separately from the others in his wallet… Better choose another restaurant, next time.)
Great insight – now we can add resistance to salt water on the list. Thanks!