I use this stuff from the dollar store (found in the air freshener/cleaner section)

I find that it helps reduce the amount of condensation build up. One in the spare wheel and one in the rear right pocket of my civic hatch.
The best way I have dealt with the moisture was to fix all the leaks in these old Hondas though.
Official EF CRX/Civic water leak thread - Honda-Tech
Ten minutes of driving and the windows are clear (like any other car without leaks).