What's causing the awful bitter taste in my mouth during the night when sleeping?

For some time I've noticed an unpleasant taste in my mouth, particularly towards the end of my sleep. I have a bottle of water permanently next to my bed to remove the taste when I need to.

Yesterday I had a endoscopy procedure (ie. from the mouth) to check if there is a gastric 'reflux' problem. This possibility is something my dentist alerted me to during a routine examination recently. He said there was some evidence that my back teeth were eroding, possibly due to a reflux problem.

The outcome was that I had a rather expensive endoscopy procedure completed in a private hospital yesterday

The result was good. That is, the doctor confirmed afterward that every thing was normal. That is, he could see no reason why I should be having this problem. He also confirmed the walls of my stomach and throat were fine with no tumors, ulcers and any other problem.

Any suggestions as to how I can get rid of this awful taste in my mouth during the night?

You asked : Any suggestions as to how I can get rid of this awful taste in my mouth during the night?

Okay :

1 - Don't sleep immediately after dinner ( have at least 3 to 4 hr interval ) .
2 - Consume a low volume diet specially at nights .
3 - If you feel posterior nasal discharge , take an ENT appointment for evaluation of any sinunasal problems .
4 - Use a tall pillow , or elevate the head of the bed ( about 12cm ) .
5 - Bottle of water is a good idea but don't use water , cola and coffee or tea with your meals .
6 - Avoid using too much fruit , specially sour taste fruits .
7 - Have at least 1 hr walking after dinner while chewing a sugar free gum .
8 - Stop smoking .
9 - Use less coffee and tea than you use previously .
10 -I'm sure! that you brush your teeth at least 3 times a day ,aren't you !? .

I get it more when I drink coffee to close to bed time, but any caffeine will do it as in coke etc, also smoking doesn't help either.But it is reflux from these things.

Do you brush your teeth and then rinse well with plain water just before bed time? If not, it helps. Anything with sugar in it will do this to me if I do not get rid of it before falling asleep.

Sleep with your mouth closed, and tell your husband to quit defecating in there.