Stop, pull the car over and have a proper rest. Being late and alive is better than being in an accident and (perhaps) dead. In Australia we have "Driver Reviver" stops along some highways - sometimes it's just a picnic table and a water fountain, but at least you can stop and relax for a while.

If you are sleepy while driving, you should stop by to have a walk, wash up and have short nap. Find something to chew and listen to some energizing music. Find a place to sleep if you really can't stand the sleepiness. Driving recklessly (including driving while you are feeling sleepy) is an irresponsible act!! It will not only endanger the life of yourselves, but also other road users.

I turn the radio to some upbeat dance music. Then I sing along and dance in my seat to keep me energized! ^^

I have to admit that I carry a bottle of energy spray in my purse, and some caffeine gum in the car. I am not a coffee drinker, so all I need is a little to wake me up. Before these things were available, I used to do what Peachey suggested (pull over and rest). Having said all that, getting the proper amount of sleep in the first place helps me to not feel drowsy during the day.

Hi... Don't drive if you feel tired or sleepy...