The worst time of day to drink is lunchtime. Just a single alcoholic beverage at lunch can significantly impair your ability to drive and even cause you to flunk a roadside breathalyzer test, reports HealthCentral of new research from Great Britain that was published in Occupational and Environmental Medicine. The effect that one drink at lunch has on your mental state is exacerbated by the natural dip in alertness that affects most of us in the afternoon. And the effect is even greater for those who didn't sleep well the previous night.