Tennis

Wear a hat, cap or visor. This seems obvious until you find out that you forgot to pack one in your bag that day (as I have on occasion). So the corollary to this tip is – always carry a hat in your bag.

Wear sunglasses. Same as above.

Change your position on the baseline. Most of us tend to serve from the same spot on the baseline over and over again, without even thinking about it. So try changing your spot by getting closer to the center line or closer to the alley to avoid the glare. This has the added bonus of giving your serve a new, and hopefully confusing, look to your opponent.

Change your stance. In other words, move your feet and position your body so that your chest is facing more towards the court or more towards the sidelines. Just make slight adjustments to your stance until you reduce the sun in your face as much as possible.

Change your toss. This may mean moving your toss more to your left or right, more to the front, or more over your head. You can also try a shorter toss and a faster service motion.

Just get the ball in. Sometimes, no matter what you do, you just cannot see! This has been the case with me in just the past few days. In that situation, all you can do is try to pop the ball up and over the net and hope it lands in the service box. At least that way, you can get the point started and hopefully beat your opponent with your other incredible moves.