Why do you bother? Just leave them be, some of them are fakes.
My friend once did the same thing and the 'homeless' man somehow managed to pickpocket his phone at the same time. Sometimes it's best to not bother.
Why didn't you eat the chips?
A lot of well meaning people will buy a homeless person a sandwich and a bottle or coke. Depending on where they are and on people's generosity this can quickly mean that they are no longer hungry. Personally I'd rather give them money to buy things they need. If they spend it on booze or drugs that is their choice.
The first guy was not hungry because he had just eaten some pizza; the second guy was a drug addict.