Stephanie Simon has this story in the WSJ on fast food in the joint.

Selling the inmates burgers and fries has various pros and cons, as described in the article.

So who pays the bill? Some spend earnings from in-prison jobs, and we are all in favor of prisoners working. Some, though, have their happy meals paid for by family from the outside. One woman is apparently spending $250 a month for her brother's burgers and fries. I suspect there are more worthwhile things she could be spending her money on.