Snickers bars. Lots and lots of Snickers bars. Seriously. For 24 to 48 hours, it won聮t do you the least bit of harm. They聮re full of calories and even have some protein. They keep for months. And, they聮re delicious.
GU Energy Gel

I聮m being only mildly facetious. I can recall plenty of times when I聮ve been on a hike or a bike ride and have bonked聴light-headedness, fatigue, slight tunnel vision, the whole works. Eat a Snickers, and in five minutes I聮m cured. Plus, I did search-and-rescue work for years, and a Snickers bar or three were always in my pack as my emergency food supply.
That said, the list of things you can take is long. Dried fruit. Nuts. Energy bars (you now can buy a Snickers-like energy bar called the Marathon, and they聮re wonderful!). Energy gels (those little things that come in Mylar packets and sell for about $1.50 each聴perfect for a quick energy hit). Those little things you can buy at the grocery store with crackers and cheese. Heck, military MREs if you can stomach 聭em.
Make yourself a food packet that includes stuff from the list above and some hot items such as hot chocolate or dried soup, or even a freeze-dried meal (surely somebody carries a stove聴if not, somebody ought to, if only to warm up IV solutions on a cold night). Put it all in a gallon-size Ziploc bag and toss that in your freezer. When the pager goes, throw the Ziploc bag in your already packed pack, and you聮re out the door.
And have fun!
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