She said the most important factor when considering an appropriate sentence was the need for deterrence and denunciation for future use of drugs and possession of alcohol.
Private Aldridge needed to be held accountable for his actions due the "serious" nature of his offending.
She and the panel accepted their were no aggravating features relating to the offender but took into account mitigating factors. These included his service record, his early guilty pleas and personal issues.
Judge Gaskill also acknowledged Private Aldridge's parents were present during the proceedings.
She said the decision had been "difficult" but there was no place for drugs in the New Zealand Defence Force.
"Using drugs totally contravenes Defence Force ethos and values."
She told Private Aldridge he was being given a chance to earn back the respect of his colleagues and make the best of this opportunity.
"But if there is any reoffending you will be dismissed."