I still tend to drive with them on since I feel blinded by the sun in the morning. However, on mornings when it is partially cloudy out and I did not get a lot of sleep, I drive with them off because this will help me feel more alert than if I was shielding what little sunlight was available.
Read more at: http://gizmodo.com/the-scientifically-best-time-to-drink-coffee-1460030914