Blow on it
Sometimes, you need to simplify your methods and go back to basics. You can ask your parents how they cheated when they were at school, and they will most likely tell you that they didn’t. But they probably used this method to do it.
Be hold the old trick of writing notes on a piece of tissue. You will need to fake that you have a cold or allergies, which will justify the cheat sheet. After all, no teacher would dare to open a used tissue. Just make sure not to use it actually to blow your nose.