Magic Tricks

Easy to do. The weight allows a great hands free turn over as shown. Innocent looking.
No, there are no threads inside the cap - could have been a nice addition. No, there is no ungimmicked cap.
So What?
It looks innocent enough, you use it, maybe pull it off an empty water bottle, do the trick, accept the comments about how brilliant you are, and do another trick.
No need to switch, no need for an examination. Do it, amaze the spectators, and move on.
Blackstone didn't pass his floating light bulb around and an tell people to examine it, it's an ordinary light bulb!