Well, it depends..doncha like that!

If the plugs have a many miles on them, just change them. They're not that expensive, $2.50 each, or if you're broke, pull them out, heat them with a propane torch to burn the wet gas off ($19.95, or $1.00 of propane, if you already have the torch) and put new ones in later. It's really not enough gas to be worried about, but enough to keep the car from starting.

In either case, my experience is that you need dry plugs, and no amount of trying with wet plugs will clear them enought to start ( Disclaimer: This is based on 1 problem with one 850, and the same thing with one Passat, one time. Your results may vary :-) )