This is the advice we used to give customers from the Oakley goggle clinic:
If your goggles have crap on the inside: get a bowl and fill it with some luke-warm (not hot and not cold) water along with a few drops of dish soap (doesn't take a lot). Take the lens out of the goggle frame and dip and swish the lens around in the soapy water for a couple minutes, whatever you do, DO NOT rub/scrub the lens. There's an anti-fog coating on the inside lens and it gets soft and smears easily when it gets wet and then you'll never be able to get the smears off and you'll ruin your lens. Rinse the lens off with again luke-warm water to make sure that the soap's off. Shake off the lens and let it air dry completely, don't hang it over a heater/blow dry it/hang it over a fire, the lens will melt.
If you have some small water spots on the inside of the lens once it's completely dry, use your CLEAN dry goggle bag to very gently rub/dab the spots off.
If they are Oakley goggles and they're all smeared on the inside already, you may have to just break the lens apart because if they were wet and you rubbed them, you scratched/wiped the anti-fog coating and that causing permanent "gunk" looking smears.