Best way to clean that nasty thing is to submerge it
in a bath of 90% ISO alcohol for a few hours, and then
grab a brush, a piece of wire (to wrap paper towel around
to scrub the inside), a few paper towels, and that alcohol
and clean the hell out of it.
Just keep in mind that when you inhale (God forbid
), tiny
droplets of that water (or ice cold vodka, etc.) gets carried
into your lungs right along with the smoke. Try placing a small
piece of paper towel over the mouthpiece when you take a
puff, and then you can see what's been making you cough.
Depending on the size of the hole in the mouthpiece, you
may be able to use an off-the-shelf cigarette filter. Don't
ask me how I know, but it helps a ton, and other than saving
your lungs you'll never notice any difference in whatever you're
smoking's performance.