I like to leave coins in vending machines
Why do you leave coins in vending machines?
It's like an psychological experiment, I am a fan of psychology and I want to see what happens here.
You shouldn't just throw away your hard earned money. You should learn to spend it in more meaningful ways.
It's just some spare change and I want to see what will happen with it.
If this topic is fascinating to you, then you should spend  you money and do a formal experiment. It is not okay to use people in this way.