Drink/eat off/from/in a cup/bowl/plate
I would say the preposition used is determined by the position of the food/drink.
Your cereal is in a bowl, so you eat it out of or from the bowl. Similarly your coffee is in a mug so you drink it out of or from the mug.
Your meal is on a plate, so you eat it off [of] or from the plate.
From works in both on or in situations because it is a preposition that indicates the source or origin of something.
Off [of] only works for on situations because it is the opposite. Similarly for in and out of.