It can work in many ways. In my country(India), it was common for people to collect subsidized rations and sell them to hotels. Hotels get the rations at subsidized prices, and people make money on the free rations they recieve.

You could also see food stamps as a parallel currency. You get work done, you fix the payment as N food stamps. The guy who takes this, uses the same method to pay others... and so on, until the final guy in the chain exchanges those N food stamps for actual rations. This has other side effects, since there is a parallel currency, it can't be regulated, its supply cannot be controlled. You can't levy taxes on it and so on...

These sort of parallel currencies already exist in India.