If one wanted to have a reasonable depiction of iron ration in the fantasy world, what form would they take? I like my fantasy realm to be about a half-bubble off plumb. That is, I want them to be familiar enough the typical player knows what they are, but fantastic enough to give a bit of flavor beyond real world equivalents. So like every struggling referee, I stole some ideas I really liked!
Qith'Pa: elven iron rations consisting of bars of pressed dried fruit. I always pictured these as tough and chewy like jerky but very sweet. Not the best meal perhaps, but more satisfying than more common forms of iron rations. From Weis and Hickman's Dragonlance series of novels.
Lembas: elven iron rations that were at once savory and satisfying. Just one portion of one cake would sustain a man-type for a full day's march. I always pictured these as faintly magical and retaining their goodness so long as they were kept in the green leaf wrapping. From Tolkien's LotR series of books.
Cram: (or possibly Kram, I pronounce this with an "ah" as in "yahoo") small seed cakes about palm-size. I always pictured these as looking vaguely like compressed cakes of birdseed and having a faintly sweet and spicy taste. These are sustaining but leave the typical person feeling vaguely dissatisfied. I'm having a deuce of a time tracking this reference down. I seem to recall these are gnomish in origin from Brook's Shannara series of novels. If you remember better than I, please let me know, google is singularly unhelpful in this instance.
Mundane: dried sausage, dried smoked jerky, dried vegetable bars, dried fruit, smoked nuts, hard cheeses, twice-baked biscuits. These will be wrapped in waxed paper and bound with twine, often with protective runes inscribed upon them. These are available in just about any settlement of size, and can be produced rapidly from supplies on hand if not pre-prepared. These are filling and somewhat satisfying, though dissatisfaction increases with each consecutive day of this fare. After a week of iron rations, reduce NPC morale by -1.