What's inside the "I <3 mustache" mug in the manor's basement ? I thought it was sugar cubes, but the text suggest otherwise. It's not alcohol, so what is it ?

The text just mentions Roxy drinking in the basement because the mug reminds Joey of Roxy drinking, I don’t believe the text suggests there’s anything alcoholic in it as far as I recall. It always seemed marshmallows to me, but honestly? I bet it’s tiny dice.