While I rarely swim with goggles my wife and I are frequent divers and snorklers and over the years I have used spit, Rain Ex Defog and highly dilute baby shampoo I have learned they are merely treating the symptom not the disease. The two keys to a clear diving mask are first never letting water get in, even a little. The second and most important is to keep the lens SURGICALLY CLEAN. Similar to water not starting to boil if there are no nucleation points (though the physics is different) an extremely clean mask will almost never fog if you don't let any actual water in. Another key (most associated with snorkling) is when surfaced with your head out of the water, usually talking to your snorkling "buddy" about the cool manta ray etc you saw face away from the sun, the greenhouse effect will heat up the air in your mask and make it more likely to fog when submered plus don't wear your goggles/mask on your head before going in put it on at the last minute it prevents that hot lens/colder water shock which can fog them instantly.