I was joking but I do really like pop tarts. Smores ones are amazing but pretty much all flavours are good. I don't think it is very easy to eat healthy 3 meals a day for $20 without refrigeration. Depends how much you need to eat I guess.

Presuming I have a grocery store in walking distance I could use them as my refrigerator. They usually have some precut fruit bowls that aren't too expensive, maybe 5 bucks. That could be breakfast. While I am there I can pick up some kind of trail mix- nice assortment of nuts with dried fruit and raisins. That could be lunch if needed or replace lunch by snacking on it every couple hours. That's not very expensive. And for dinner I could wait until the stores hot prepared meals are put on discount for the day. The stores near us sell them 50% off when they are closing up the ready to serve section for the evening (around 8pm) so you could get some chicken and rice or potatoes or some nice mac and cheese etc for pretty cheap.