They use them in MREs to extend shelf life using some sort of sugar/preservative solution. You could make your own by soaking raisins in warm water/sugar or fruit juice until the plump up and keep them in the frig.
Seems crazy that in our world, where people can buy and endless array of products, that MRE packages and the ONLY place to buy these things. And by the way, if you have not tried them you are really missing out.