I have had lawyers who frequent my restaurant say to do this as a last ditch measure to avoid a DUI. However what they suggested to do was pull the keys out of your ignition, drop them on the floor and when the cop comes to your window drink what you have. It becomes harder to submit a breathalyser test in a court of law if the cop sees you drinking while not operating a motor vehicle (throwing the keys on the floor). However,I wouldn't suggest putting yourself in that situation.