When I wake up after sleeping on a train or a bus or in the back of a car, I often find an incredibly unpleasant taste in my mouth. It seems as though a few people get this - google has various results for a "metallic taste after waking up" - but I've not heard any word to specifically describe this taste, as in:
I'm just going fetch a drink - I slept on the way down here and my mouth tastes of something
Of course, "my mouth tastes of crap" would get the point across handily, but I'd like a word that literally refers to this specific sensation. Phrases are also welcome. British english is preferred, but I'd happily borrow from other dialects.