There is a most definitive cure for sinusitis. It acts immediately and cures within 24 hours. It also might kill you as it is highly poisonous and high doses create an allergic reaction at the upper respiratory tracts. First the cure, then the safety protocol:
Step 1: Find Acı Düvelek (or Kavun), known in English as Squirting Cucumber (Lat. Ecballium elaterium)
Step 2: Squirt the fresh juice of a single fruit into a glass
Step 3: Apply two drops of the juice into each nostril and sniff it deep into your nose
Step 4: Sit back, relax, and the sinus cavities will drain drop by drop in the next twenty four hours. You will feel relief within an hour.
Safety: Do not apply more than the recommended dose. I tried a teaspoonful of juice in both nostrils and the allergic reaction shut down my nasal cavity along with my pharynx. I could not breathe and had to be taken to the hospital for emergency antihistamine and cortisone shots.
Despite my new found enthusiasm against waterboarding, I am a huge believer in this plant. I went back to the cure in August 2009 after first using it some 20 or so years ago. Also just edited the wikipedia entry for Acı Düvelek after finding clinical studies on it – the story is now official. Turkish ekşi sözlük also talks about the folk remedy.