Dilemma in a trust situation – when is it criminal breach of trust

I have been reading up on the textbook for Equity and Trust by Pearce and Stevens at my own leisure during my period of leave of absence. I do get the concept of what a trust is about, and the various variables to which the trust can be formed. Basically, a trust is a legal instrument by which a person (settlor) bequeaths the goods to a trustor who administrates how the goods is to be dealt with for a beneficiary. One instance of a trust instrument at work is a will, which specifies how the inheritance is to be given out to the heirs after a person’s death. There are variables construing the nature of a trust, such as whether it allows the trustee to allocate the goods to the beneficiaries at his own discretion (discretionary trust), or is required to follow the fixed allocation stipulated in the trust instrument (fixed trust), or has complete discretion whether he wants to allocate the goods to the beneficiaries or not.

I was having some sort of mental burnout for law school for this semester as well as the previous semester such that I was unable to conceptualize and understand anything from my reading at all. And one thing that I find myself struggling in law school is to be able to read and understand the copious amount of readings fast, and to make my own notes for the examinations. But when I read it on my own leisure, I am able to understand things eventually.

I was thinking how the law of trust would work in a scenario which I had while I was in the army. As an administrator of a course, I had to order beverages for the members of the course using an electronic online system. When the beverages of water arrive, I would store them somewhere in the office or the storeroom. My dilemma was whether I was allowed to consume the beverages, or whether that would amount to a criminal breach of trust. It seemed intuitive to me that it would be an offence if a staff would take the entire supply of beverages home for his own consumption, but what about if he just takes one or two packets from the entire provision? Would the law distinct whether the taking from the trust by the trustee for his own benefit is trivial, or will it hold the trustee absolutely to his fiduciary duties to administrate the provisions for the beneficiaries?
My understanding of the situation is a little unclear. I am not sure whether I am even miscomprehending this as a trust situation. I have been rather bad when it comes to understanding law stuff.