Someone takes the money and leaves the cans. Maybe they ripped open the bag and made a mess.
Maybe someone fights over the bag when they both see the money inside it or word gets out and now you have a bunch of mentally unstable people coming to get your cans. Not to be a NIMBY, but they are generally not the kind of people you want to be around.
I think that money would be better spent donated to a homeless shelter or the food bank or some other ngo helping street peeps. Good on you for trying to help out though.