I got one of those as a birthday gift in grad school, and it's a lot of fun, even 10 years later. I used to fill (yes) mine with tinted water for added joy.
It's a giant pain to get anything out of them, though, or, for that matter, to clean them (unless you have a trick for it?).
You betcha, yew bet TeePeeTee! I use two magnets, each covered with chamois cloth. Even then, it's a challenge.
I don't own one, but as far as getting liquid out inverting the bottle and siphoning out of the bend seems like the easiest way.
I think that would fail because air wouldn't be able to get into the bulb. If you've got a tube for siphoning I think a better strategy would be to blow air in thus pushing the water out.
And, I'll bet, you've done some research in the nature of small ecosystems growing in almost-closed bottles...