There's a couple of long-distance drivers on here whose opinions carry a lot more weight than mine, but....
I've done the cross Canada drive several times as well as regular 15 hour drives to see family.
Drink lots of water. Get some podcasts or spoken word books. Sleep when tired. A 45 minute nap does me more good in the long run than an energy drink. Energy drinks get me thru the last 3 hours of a long drive, but leave me in worse shape if I use them to get thru the middle part.
Pace your speed in the first half of the trip. Yes, you can drive faster but the fatigue factor goes way up, you'll pay for it in hours 10 and 11. Cruise control is your friend, set it the speed of traffic and make up the time when there's no traffic.