Day 22 and just got over a week-long struggle with this, including horrible breath, a disgustingly coated tongue, and a painfully parched mouth. I tried an oil draw (I'd never tried this before) out of desperation, and had excellent results.
Before I started, I was beginning to think I'd never salivate again and the stench in my mouth was bad enough that it would wake me up at night. Within a minute, the salivary glands were pumping out plenty of juice. I went for 20 minutes, washed my mouth out, and tried to go back to bed.
Instead of diluting the stink, the saliva seemed to magnify its effect. It kept me awake for another 45 minutes or so, but all the time, my tongue was resting in a nice comfy puddle of saliva. (Funny how you appreciate the little things when you haven't eaten in 22 days). To make a long story short, the coating on my tongue started to come off in small hard chunks maybe 1-mm in size. I attacked my tongue with the electric toothbrush (which had no effect previously) and within minutes, half my tongue was clean for the first time in at least a week.
The next step will probably be frowned on, but I alternated gargling full-strength hydrogen peroxide and mouthwash for a few cycles. Within 15 minutes I had something approaching a clean, neutral-smelling mouth.
About a day has elapsed, and my mouth hasn't been parched once. Small chunks in the very back of my tongue are still dislodging from time to time, and if any bad breath remains,I can't detect it.
This was by far the hardest part of my first 30-day fast. I'm not quite sure I buy the whole reverse-osmosis argument used to motivate oil pulling, but for whatever reason, in this case, it worked like a charm.