Occasionally I have to get up very early for flights, surveys etc and only get a couple of hours sleep. As soon as I wake up, my throat feels completely dry and I am extremely dehydrated. The only way to put it right is to drink silly amounts of water.
But if I was to get a full 7/8 or so hours sleep rest (i.e. longer without water), I do not feel this and am not thirsty at all.
Any ideas why this happens?