Update: The manufacturer writes, "Sea Gold is NOT for use with swimming goggles. It can irritate the eyes and we would appreciate it if you update it with our Anti-Fog Spray.
For the record, I haven't experienced the irritation, even after more than a month of use.
I am an extremely dedicated swimmer, thanks to a chronic pain condition that is just barely held in check by an hour in the pool every day. I go through a couple pairs of goggles every year: generally the thing that goes first is the elastic or the ratchet for the headband, but sometimes a pair of goggles will get so fog-prone that I just can't swim with them anymore.
There's nothing like a fresh pair of swim goggles. The manufacturers coat them with some kind of gel that prevents them from fogging better than any product I'd ever tried (and I'd tried a lot of them). What's more, whatever this gel is made of doesn't sting if it mixes with water that seeps in and then gets in your eyes (a bunch of anti-fog products I've tried appear to be dilute dishsoap that stings like crazy).
After literally years of trying different products (Cat-Crap, Liquid Spit, etc), I finally found an anti-fog concoction that actually works: Gear Aid Sea Gold Anti-fog Gel Coating, which appears to be the same stuff that manufacturers coat their goggles and masks with at the factory. Just put a tiny bead of it on each lens, rub in with your fingertip, rinse a couple times, and you're good to go. No fog forms, not any, and even after a month of using this stuff, there's no visible buildup on the inside of my goggles.
The stuff is sold for SCUBA divers and I'm definitely putting a tube of it in my dive-bag the next time we go on a diving holiday. In the meantime, This $9.02 little bottle is everything I've been looking for in an anti-fog treatment for my swim goggles.