Officers are trained to use their nose to smell for the odor of alcohol during a DUI/OUI investigation. An Officer isn't really smelling alcohol during the investigation, but congeners which are flavorings put in alcohol to give the product a particular taste.  For example, hops flavors beer.  If you are stopped by an Officer and you have been consuming alcohol prior to driving, never admit to drinking.  I reviewed a case last week that would not have resulted in a DUI investigation if the client had not admitted to drinking a couple of alcoholic beverages prior to driving.  In this particular legal situation, you should maintain your right against self-incrimination by not answering this question.