My favourite riding sunglasses are my Bollé Mamba II safety sunglasses - they're light and wrap around properly while being by far the most comfortable ones I've found. They're also cheap.
There is a downside, which is normally only apparent in winter but was a bit of an issue yesterday morning: they fog easily, especially on the bit I look through using the drops or aero bars. Yesterday was sunny all day, but I started before it warmed up, so I was out in around 10°C, sweating a little. It's possible wind chill on the outside was cooling the glasses, as I averaged >30km/h for the hour or two this was a problem, before the day warmed up. This wasn't about stopping, because I didn't, but when rolling along. It was better when riding into the sun, but that never lasted long.
I like the way they sit so close to my face, but it means that unlike my less-good cycling-specific glasses there's no airflow behind the lens.
The issue may be what they call "upper protection". They're a sort of frameless design, but with a little ridge running along the top of the lens, at eyebrow height and touching my face. It's visible (just) in this photo of them upside down:
They're getting a little scratched and it's nearly time for a new pair, so it's a good time to try some experiments. Is there some way I can increase the airflow behind the lens? Are there designs that do this so I can be inspired? I don't really want to try a coating, because I'm likely to wipe it off.
Other, looser fitting and less comfortable glasses don't fog up nearly as much (including another Bollé polycarbonate pair, so it's not the material).