There is a pilot program running in Massachusetts right now, there may be similar ones in other states:

For those who are SNAP beneficiaries there is some kind of benefit gained for buying qualifying fresh food- the easiest examples being fruits and vegetables, obviously [frozen count but canned don't].

You get a certain amount of benefit/credit added to your SNAP balance for each qualifying purchase.

I think this is pretty great because it is true that fresh and healthy foods can cost so much more- if you already are on food stamps it is so hard to stretch your budget and include a lot of healthy options.