My VW golf has a large enough holder in the door for a 1L nalgene bottle. It's AMAZING. I rarely drink from it while driving but I often take a large bottle of water with me wherever I'm going, just so I have it to drink from at my destination, or whatever. For example, each of the past 2 weekends I've driven an hour each way to a trail race and have lots of water when I arrive. I suppose I could just let it bang around in the trunk the entire journey, but having it secured seems far more civilized.
This means that even when you can't pull over to get a drink, you can always reach down and get water. However, the regular cupholder remains free if you get a coffee or whatever.