So the Army rules on Art 15 require that the commander not find you guilty unless the evidence is "beyond a reasonable doubt"
That sounds great...the same standard you get at court martial
The problem you have is that the commanders will not always apply such a rigorous standard.
In fact, in my experience, in all services, it is very rare for a soldier
to be found not guilty at Art 15.
The main reason for this is, in my opinion, tied to the reasons that commanders use Art 15. Art 15 is use (again, in my opinion) by commanders for the good of the unit. They use it to send a message about what conduct will and what conduct will not be tolerated in a unit.
In my opinion, if a commander has a real concern over the guilt or innocence of a solder and want them to receive a fair trial, they send the case to court martial.
The rules of court martial, including the rules against hearsay and rights to confront evidence do not apply at art 15.
So they can convict you of the policy or order (the 2 drink rule) even if they do not have solid evidence of 2 drinks.
If your goal is to win this? I would take the court martial. Make them prove the case to a jury or a judge with all the rules of evidence in place, and a proper use of the beyond a reasonable doubt burden
On to your question....
How can you fight this?
Well...you can testify, testify you had only 2 drinks
And you can bring in an expert (you may have to some digging around for this one, perhaps TDS can help) that can talk about metabolism rates for alcohol in the body. Based on your body size and time of drinking, it may be that an expert can say that .109 is possible with two drinks. You need someone who understand metabolism to do this for you. BTW, if you go to court martial, I would expect the court to order the command to pay for such an expert. If you go to art 15, you will have to pay them yourself.
Finally, I would find someone at the command who can testify you were not at QRF...what you say that should be easy...and that is the reason I would refuse art 15 and take the court. If you can prove that you were not in violation of the order? I would not risk art 15.