Article 112, UCMJ, covers the criminal offense of being drunk on duty.  It's not a common offense that I have seen over the last several years that I have specialized in court-martial defense, though it is something that will be preferred on a charge sheet from time to time.  Typically, a Specification under Article 112 is preferred in addition to more serious offenses such as sexual assault or assault and battery.  The specific Article is written as follows:

(a) Drunk on duty. Any person subject to this chapter [10 USCS §§ 801 et seq.] who is drunk on duty shall be punished as a court-martial may direct.

(b) Incapacitation for duty from drunkenness or drug use. Any person subject to this chapter [10 USCS §§ 801 et seq.] who, as a result of indulgence in any alcoholic beverage or any drug, is incapacitated for the proper performance of duty shall be punished as a court-martial may direct.

(c) Drunk prisoner. Any person subject to this chapter [10 USCS §§ 801 et seq.] who is a prisoner and, while in such status, is drunk shall be punished as a court-martial may direct.

As stated, because it is an offense that is typically charged in conjunction with a more serious offense, defending against it does not take precedence in my trial preparation.  There are typically witnesses to this offense which make it much harder to defend against.  When you think about it, you are only being charged with the offense because people interviewed by law enforcement observed the accused in a state of drunkenness.  So, the accused is already facing an uphill battle with this offense.  If it is possible to show the actual BAC of the accused, that can serve as a good defense.  If this is not possible with the lack of evidence, then the subjective observations of those accusing witnesses will have to be attacked, i.e., elicit evidence how the witness was stone cold sober, had a bias against alcohol, etc.  The expected punishment for an Article 112 offense is generally light, so your attorney will likely be more focused on beating the more serious charges that have been preferred.