Eating in the car during long hauls is an unfortunate requirement. The less stops for food/pee the better.
It's the only time it happens in our cars, and we're super anal about it.
Any drink requested by the driver gets cracked open by the passenger and presipped to avoid spillage (I'm typically the passenger except for maybe 2-3 hours of the trip - Mike is hardcore when it comes to driving long distances). The drink container is usually wrapped in a paper towel to keep the condensation from wetting the cup holder, and also to absorb any stray drips. It also dampens vibrations so the drink container doesn't rattle.
Our favorite road snacks are Cheez-its or cheddar Goldfish, sour cream and onion Pringles, Rice Krispie Treats are a DEFINITE MUST, and chocolate covered pretzels. Drinks of choice are Mountain Dew, Coke, Gatorade G2, bottled water, and an occasional energy drink (Monster or Red Bull).