ClearCoat Anti-Fog Spray

This is the most effective spray-based option here, with a coating that genuinely lasts several days rather than fogging up again after the first few uses like some cheaper sprays. It works across glasses, ski goggles, and swim masks equally well, so one bottle covers multiple uses rather than needing separate products. The only real downside is needing to let it dry for a couple of minutes rather than being instant, though this is a small trade-off for the extended effectiveness.