Drinking and driving is dangerous, and that applies not only to alcoholic drinks but to all manner of beverages. Heading Insurance.com's list of the top-10 most dangerous foods to consume while driving is coffee, which (as you may have noticed) is not only damp, but can be exceedingly hot. There's nothing that induces mad swerving (and uncontrolled profanity) like boiling hot coffee in your lap. Also making the list of killer foods are soft drinks, due to both spillage and something that Insurance.com calls an unacceptable risk of "fizz up your nose" [source: Borroz].
What this means is that it's probably not a good idea to eat or drink while driving. And nothing says "I drink and drive" like the addition of an aftermarket cup holder. As if there wasn't already enough chance of you dropping your drink in your lap, add to it the chance that your jury-rigged holder will detach from the vent where it hangs by the smallest of hooks and become something else to roll around under your feet.