In Europe where people get their deposit back for bottles, the homeless (interestingly, not just them, a study in Germany said it also gave bored pensioners something to do) look in trash cans to find bottles to return. I remember reading an experiment where a city (I think in Canada) implemented a trial program to give people 6 cents per cigarette butt: they spent the money marked for the returns quicker than expected because the homeless people collected butts diligently.

It's a bit of a crazy world to make the homeless clean up pollution other people make, but even without this program there are (and will) still be homeless people...