I've tried cleaning and had mixed results. Depending on the reason to clean will usually determine the results.
If it's for changing flavors I soak in vodka for a couple of hours to over night then let it air dry for at least 24 hours. If it was a really strong flavor, sometimes it never goes away.
If it's because the coil isn't performing then its a crap shoot. Most of the time if the cotton isn't providing flavor then soaking never really brings it back. My opinion, you results may very, if you have vodka laying around its worth a shot. If you have to go buy vodka it maybe cheaper to just buy the coils.