I haven’t read Dune since high school, so correct me if I’m wrong, but I feel like the books were rather vague regarding how exactly the Fremen/deathstills got the water out of someone’s body (some sort of vacuuming/filtering action is assumed). The movies I’ve seen more recently, and they also kept an air of mysticism around the ritual.

Dune: Awakening gives you a big syringe and a bag and sends you to work, like a vampire saving snacks for later. It’s just the way of life on Arrakis, but that does mean at some point in this universe, some lunatic had to be the first one to say “what if we sucked out all their blood?” and everyone kind of went with it.

Gotta do what you’ve gotta do to survive, I guess.