I'm not going to give my friend $20
Why don't you want to give it to them?
I just don't want to give them money.
It is your choice to give a friend money.  I would need more context to understand why you do not.   It would be good to help someone truly in need and also to avoid enabling someone or being used by someone.
How will I enable them? If I give them money then how can they learn how to make money themselves?
While friends need to be there for each other, you don't have to support them with  money if you don't want to. It would be good to explain to them why you can't.