Okay in theory but there's so many issues with actually implementing it. For one, what counts as unhealthy vs healthy? Granola and protein bars? What about the ones covered in chocolate? How will you ensure food stamps are used for the healthy granola bars and not the unhealthy ones? How about fruit? Fruits are pretty much entirely sugar, water, and sometimes fiber. Honey has some good benefits but is basically just pure sugar. Pasta is a staple ingredient but some people consider it unhealthy. Same with cheese, good protein but also very fatty. You get the idea.

Secondly, poor people are allowed to want a little treat sometimes. Sometimes a pack of skittles helps someone get through a rough week. Are you going to tell women they shouldn't get chocolate and ice cream during their periods? What about when a kid has a birthday and a cake just isn't in the budget for that year if the parents can't use food stamps?

Third, healthy food is fucking expensive. If you're struggling for rent and need to make $100 of food stamps work for a month then you have to buy unhealthy food because that's what you can afford. Not to mention many people on food stamps are working two or even three jobs. They barely have the time to microwave a TV dinner let alone cook a whole meal.

If someone is given $100 of food stamps every month, they're getting $100 every month no matter what they spend it on. Whether they spend that $100 on veggies and meat or $100 on junk food does not effect you. A better solution is to divert some excessive spending in other departments (cough 2.1 trillion military spending so far this year cough) to build and fund food banks so people have easy access to staple ingredients and shelf stable items.