if you can find Miso Paste, or even instant Miso anywhere, that's usually one of my go to's. I'd stick to white miso cuz its more bland than awase or red miso. Just put like a tablespoon in a mug and put hot (not boiling) water over it and stir. It's yummy and got salt which might help you absorb water better and save off dehydration. Depending on where you live, you might find miso paste in the refrigerated section of the supermarket
Pair that with a hard boiled egg for a bit of protien and thats usually what I do.