Are you still singing the same old hand washing song? Are you tired of it, yet? Write some new words to fit with your favorite melody.
Maybe it’s the tune you are tired of. If you are musical, compose a new one, and write down your composition; if you can’t do that, choose a new tune and amend the words as required.
Teach the song to the others you share a bathroom with.
(Rinse, and repeat this process whenever you need a change.)