On both of my water only fasts (9 day and 15 day fasts), I had sinus drainage. The first fast, I developed a constant nasal drip - it was not thick, or discolored, just constant. The second fast, I felt a sinus drainage come down the back of my throat. This also was pretty connstant. Both of these appeared after day 4 or 5 and remained for most of the fast.
I have learned, mainly through reading posts here, that often the areas in your body that are holding the extraneous tissues, toxins, arthritic build-up, plaque etc. etc. will be the very areas where you will experience a great breaking up of these materials and they will vacate the body in a variety of ways, nose, throat and tongue, urine (obviously) and bowel movements, skin, etc.
That has been my experience. You sound like you are getting some serious crud out. Have you ever been diagnosed with sinus or lung problems? Are you a smoker or ex-smoker? My doctor had been telling me for years and years that I had awful sinuses...but quite frankly, I never felt like they were so bad. But I could see during the fast, that there was definitely some build up there. How long do you fast for? I would consider a Bragg protocol for periodic quarterly fasting to see if that would finally eliminate all that stuff. Also, you could save a wad and have it analyzed just to be sure there is no evidence of disease. My stuff has been pretty clear, but if it was thick and smelly I think I would opt to have it checked further, but that could just be my inexperience.maybe some others have some better advice for you.