The white noise from the wind, the drone of the engine and tires on the road, the constant, dull focus on a point in the distance ... it all adds up to a very lulling experience.

Pull over somewhere, put the seat down, set a timer, and take a 5-10 minute nap. It does wonders.

Open the window so you have some fast, fresh air on your face.

Driving while drowsy is at least as bad as driving while drunk or on drugs. As others have stated the best thing is to find a safe place to pull over and catch some shuteye. Nashes and Ramblers had an advantage for this since the front seats folded flush with the rear to form a bed. (Nash actually used to advertise that as a way to avoid motel bills!) Problem though as a young man if you drove one of those cars dads would not let their daughters go out with you.

Chewing gum is very helpful. I used to work 12 hour night shifts and had a 60 mile commute home at 5AM.

I concur with the nap. That works best. But often times I am in the middle of nowhere and need to get to the next safe spot to turnoff. 

I’ve tried opening the window briefly for some wind and fresh air. Turning on the AC fan full blast. Slapping myself silly. Loud music. Anything to break the monotony. It works, briefly.  But the I get drowsy again.

Best thing to do is pull over and take a nap in a safe spot, IMHO. 

I have chronic insomnia. For the past year or two, I have struggled with falling asleep at the wheel. It is not a good situation and for me, stopping to take a nap isn't viable.

I definitely empathize with anyone having this issue let me tell you. I've had to make some last minute saves that I'd rather not repeat. Honda's Lane Keep Assist also been a priceless help.

First off, if I start getting the idea that it would be nice do close my eyes for a moment, it is time to follow some immediate advice from above, like rolling the windows down, singing, whatever that will help immediately. If I know I only have an hour or so until I am home, this normally only happens on my multi thousand miles trips, I crack open my emergency bottle of mountain dew or mellow yellow that I always pick up while I am at a gas station. That stuff wakes me up way better than coffee. It only works for a fairly short period of time for me though, maybe two hours at best. If I am too far from home, I find a good trucker/travel gas station, fill up the gas tank, and find an out lying parking spot to nap for a bit.

It also helps me to remember what happened to a cousin of mine, around 1990.

He was very tired from work, and driving his big Z71 Chevy pickup on an interstate, he fell asleep and rammed the back of a semi.

He didn't die immediately though, he was crushed, and was in excruciating  pain for hours as he made it to the hospital, and then he died.

For some reason that helps me to make sure I don't fall asleep at the wheel.

I agree on the wisdom of a nap, but barring that, what I've found helps is fresh, cold air and listening to music or talk that you dislike. Nothing keeps you awake like anger. Singing your self is also better than listening to music.

I’ve started falling asleep at the wheel many times and it’s a scary experience swerving out of the lane and not being able to tell how close you are to the cars ahead, or seeing double. The moment where you almost crash will scare you and briefly wake you up for like 5 minutes before you start to get drowsy again. I’ve also driven stoned many times (not anymore, obviously) and I’ll tell you right now that driving when you’re that tired is much much worse than driving stoned. I don’t condone driving high but I’d much rather be doing that than driving while my eyelids are getting super heavy. Pull over and take a 30 minute nap. Energy drinks are BS because they never work on me 

Many years ago, I drove semi's for two years.

The owner's and dispatcher's loved me, I was the only guy who was 100% drug free and was able to work 18 hour days back to back.

I had zero wrecks, and zero issues.  Many times I was hauling liquid hazmat loads.  

Earlier in the day, the owner I worked for had cut a deal with the union dispatcher who we were pulling for at the time. 

After working 13 hours hauling concrete with a 45ft flatbed trailer, he let me in on the plan.      

Around midnight with my tractor, I snuck into the yard and hooked up to a tanker placarded hazmat (flammable liquid).  My gross weight was close to 80k.

I took off and drove hammer down for 5 hours, performed a pump off, and drove hammer down for 5 hours back to the yard.  

I did develop a technique for staying awake, however I'm not going to tell you how I would do it.  It's too dangerous.

When you get tired, I would follow the excellent advice above and simply pull over.  It's just not worth risking your life or anyone else's life.

Many years ago I fell asleep while driving from NJ to Georgia. I was on I-95 in Virginia, about 3 AM. Hit the guardrail and spun across the road into the median. Just missed getting squished by an 18 wheeler. I was wide awake for the rest of the drive, but I don't recommend doing this.