I keep a small 2 ounce thingy of gatorade powder in the car in the summer. Flavor + calories + salts. I used to just carry those little sugar free lemonades, but I figured it made more sense to get something more out of it..

I agree with Bacpacjac completely on the coffee thing- have a few of those powdered cappuccino things in the winter; close enough to coffee for me, close enough to hot chocolate for the kids