Alcohol has no odor. It could have been non-alcoholic beer for all they know ...

Odor alone, while likely enough to investigate, isn't enough to convict without a positive breath / blood test and/or witnesses, etc.

Unfortunately, most people, especially teens, don't know their rights and furthermore their parents are ignorant too of the law / one's rights; often can't afford the representation that can make all the difference ... money == justice ... sad, but most often true.

Ron