Short of water: Suck a Pebble. This was my dad’s advice when I was a youngster. I thought at the time it was just a trick to prevent a dry mouth; something like chewing gum, but it has a more important feature: it prevents you breathing out through your mouth, THUS enormously reducing respiration water loss. It ranks with travelling by night and resting by day as prime water conservation strategies.
The Fremen of Frank Herbert’s ‘Dune’ were entire experts at this, – and at water harvesting and storage. Though it is fiction it is worth a read if only for what it can teach us about the importance of water. The famous Ancient Greek orator Demosthenes (384–322 BC), was also a pebble sucker: according to Plutarch he overcame an initial stammer by training himself to speak with pebbles in his mouth, so there might be more to be gained. Far too few folk speak clearly nowadays. Of course, this may have something to do with my increasing deafness! I actually think it would be possible to create something like a ‘stilllsuit’ to harvest the water otherwise expelled by your breath. it would require you to breath in through your nose and out through your mouth. It could somehow be incorporated in one of the gadgets below:
In cold, dry situations (such as high mountains, or the poles) a cold weather face mask can save you precious water: http://www.theultralighthiker.com/cold-weather-face-masks/