While a Blood Alcohol Test Result would be more Conclusive Evidence that you were indeed drinking, there are other ways for them to prove it.
They could have Testimony of some of the other participants there who saw you drinking.
The Officer could testify as to your demeanor/actions: slurred speech, staggering, smell of alcohol on your breath, etc.
While these may be more circumstantial, they may be enough for them to charge you and even convict you.
I'd suggest honesty, respect and show that you are indeed sorry.
It will get you much farther than being cool or disrespectful.
Good Luck and I hope you have learned from all of this...that is what the Judge will want to see, that you have Learned and that your Personal Behavior is changed.