The officer is not required to save evidence. However, it certainly hurts the people’s case. It’s not grounds for dismissal because technically the people can still prove the case with the testimony of the officer. I am familiar with the Court your case is before and these types of cases are very often reduced and a fine is assessed.
The liquid certainly would help the case (if it was indeed alcohol). But the police are not forced to keep the evidence. The police officer can just testify against you in court -- i.e. that he smelled the liquid and it was alcohol, etc.
That's an interesting question. The DA needs a lab report to prove that cocaine is cocaine so perhaps you can argue that the DA needs a lab report to prove what you had was alcohol. There is probably case law on this.
The above is for informational purposes only and not meant as legal advice.
In NYC they require that the officer observe an alcohol container with brand name e.g. "Bud" "Crazy Horse" "Colt 45". If you were drinking out of a cup, I don't see how they can prove the case.