I'm mostly with Oregon Mouse. I rarely eat lunch as such, but snack often on GORP and granola bars of various sorts (I'm fond of apricot Cliff bars cut in pieces). But I cook with esbit (when I'm solo). There is usually a little piece left when I'm done boiling water. I blow it out and store it in a Ziplock.
sometimes when the day is long and the weather miserable, I'll heat water with a couple of those pieces and make Cup-a-soup or hot chocolate. Almost no additional weight and a good pep up.

best, jcp