Staying awake to combat sleepiness while driving long distance - possibly to an important meeting, in which punctuality is perhaps instrumental- is not a pleasant experience.
Stack it up!
One must be preemptive!
Stack your car with a large variety: cans of coffee, espresso, tea, pepsi, chocolates, spicy chewing gums and sweets of all kinds. Chew away!
If all else fail, exit road, park in a safe, well lit, big street and take a nap.
Remember to shut windows tight, except a sliver for ventilation, and hide all valuables before dozing off.
Be a Professional.
A Professional Chewer.
