Isn't baked potato, beans, coslaw with fruit a perfectly acceptable lunch regardless?
It's when you skip lunch because that's your tea and you know tomorrow's tea is going to be shit, and the day after, and the day after....its not necessarily the food, its the lack of choice.
If they want to teach them about austerity, give them a tenner each and have them feed and entertain themselves for a week. For four weeks in a row, say. Even then it will be only scratching the surface.
It's like those charity nights where you spend the night sleeping out 'like a homeless person'. They all seem to get a bit cold but have a whale of a time, talk about the comeraderie etc. And of course it is utterly meaningless in the context of what it feels like to be homeless.