Never did that because i know an immature delivery man is gonna take as much as he can like a kid at a trick or treat
But i did give out bakkas (a small cold refreshing drink) to delivery men when they delivered in the summer

Thoughtful acts do work. I do not disagree with LazyBumi's thoughts. Yet, it's just a few bad apples who may exploit someone's kindness. While many good apples will appreciate the kind act.