For travel in the car I always make sure they have some type of moist food to eat, like fruit (grapes, watermelon, etc) and I will usually freeze a few peices of fruit beforehand to put in their carriers at the last minute that way they have something cool to munch on. I don't give them water bottles for car rides as they always end up flooding the carriers, if it is a long trip set the water bottles aside for the drive and make a stop ever two hours or so to offer them the water.
A quick trick we have found for water bottles, the standard 16 oz sipper tube attachment for a water bottle will also fit a bottle of water you can buy in the convenience store think it is a 16 oz bottle.