I have only taken this trip once LED-MOW on a night train.
I brought a bicycle chain lock, and toilet paper.
We had to buy sheets for our first class cabin. Cost under a dollar US.
The door to the cabin had a huge(3" x 18" chrome plated) latch on the inside on a thick door. It would have held off a Mongol horde. No key.
The toilet paper came in handy.
I think we were supposed to get tea in the morning, but did not.