Back when I was a starving musician and living more or less in the back of a van down by the river (some exaggeration, but not much), I couldn’t afford much in the way of food — “starving”, duh — and so I found myself eating an old boarding-school staple, a South African cereal named ProNutro. Here’s the scoop on it, in addition to what you can read at the link.
It looks like sawdust, and tastes pretty much like slightly sweetened sawdust. However, its nutritional value is extraordinary: one bowl per day, and you will not starve. In fact, if you have a large bowl for breakfast on a normal day, you may find come dinnertime that you’re not very hungry and could possibly skip dinner altogether.
It’s best eaten cold, with either milk or half-and-half (the latter makes delicious porridge of it), with a little sugar to taste. However: if times are really tough, you can use water instead of milk. It doesn’t taste that great, of course, but it will keep body and soul together. (I once lived on ProNutro made thus for just over a month, stealing sugar sachets from restaurants.)
It is highly absorbent, and even when you think you’ve used enough milk / water, you’ll still have to add more before you’re done.
I’m actually eating a bowl of ProNutro as I write this, which is what prompted the post in the first place. Try it: you’ll either like it or hate it; but there’s no denying that it works as survival food. Ask me how I know — oh wait, I already told you that.
Note: I don’t get any bribes income from any product I recommend on this site.