Today I finally took a break from scavenging, since we've obtained a massive stash of preserved, non radioactive food and supplies from the bunker "Engie" was living in.
Thus, feeling only slightly unproductive, I've set out to resolve one of the mysteries that bothered me for a while.
Coincidentally enough, Captain walked off with Engie, probably on some sort of ridiculous errand, leaving the mug unsupervised.
I've examined the underside and the inside of the mug.
No connections or seams.
No false bottom.
No coils, nothing that could possibly heat the liquid.
Ceramic. One red heart.
...Just a stupid ceramic mug.
No visible mechanisms that could possibly condense water from the air. Maybe if I watch it long enough, something will happen?
...Blasted mug! Reveal to me your trick!