During the massive riots that followed the complete quarantine of the city, the vending machines were some of the first things to get looted. Maybe it was their prevalence around the city; maybe it was the ease with which they could be broken into; maybe folks just like Twix and Twinkies a whole lot. Whatever the reasons, there aren't many intact, filled machines left in the city. If you do find one upright and unbroken, then they are very easy to pick clean. Just avoid the stale crackers and cheese.