A few times, my husband and I got panhandled coming back from a nice restaurant, and happened to have a doggie bag with us. Offering that never went over well and either got outright rejected or grudgingly accepted and quite likely not eaten.

As the article says, homeless people have ample food, due to the missions, et al. A friend of mine who had a brief homeless stint confirmed this, saying that it was easy to get three square meals a day while living on the streets. (It just takes standing in line for hours, which makes pursuing other things, which might help one get off the street, difficult.)