fun fact: water should react most strongly to the radiation used in microwaves while ceramic plates and glass should be pretty much inert - feel free to test by inserting first an empty mug of your choice, then doing the same wirh the mug filled with water and coming back to us with your findings :)

Here is a nice starting point for further reading

also as a side note: metals also react very strongly and the strong reaction of metals combined with the weak reaction of ceramic materials is why microwave kilns are a thing (for an explanation see the appropriate section here under "modern kilns")