Sounds like a poor idea to me. We already have food stamps, but frankly cash is the best solution for the small shopping a homeless can afford. The blockchain wasn't created to record all the sodas, sandwiches and beer sales on the planet. I would never use BTC to pay for any of those items. Cash is just easier.
A lot of homeless people do not receive food stamps for any number of reasons. Likely mainly because of ignorance of the food stamp program, but also because they are not eligible because of prior convictions, or they quit their job.
