I had been trying for about past year and was thinking of how could i get my rides foggy Fog lights cleared. I tried cleaning it it mild soap, glass cleaners even asked TASS guys to get it cleaned. TASS guys had a simple answer "Sir this cannot be cleaned, only option is change it.", I calmly said "Thank you, I would look for some solution".
While roaming over internet I found an article of how this could be done within Rs. 10/-, simple clean it with toothpaste. Along with my teeth
my fogs have become much clearer. Simple things that I did,
1. Cleaned lights thoroughly with water to ensure mud on and around it is cleaned.
2. Applied toothpaste on glass evenly and left for about 5 mins
3. Scrapped glass with used toothbrush
4. Cleaned it with water
Few of links that you could navigate for more details, How to Clean Headlights - wikiHow Fuel Saver: Clean your Headlights with Tooth Paste!!