Another really useful tip would have been: If you find a stream and have a bottle, fill it. Surviving is more about using all of your resources than about being "tough".
Bingo. And that's what the instructors should have been teaching...instead, it sounds like they got a rise out of tormenting their customers.
I'd say they deserve to be sued.
No kidding. Water is probably the one thing that one can’t “acclimate” to the lack of to any appreciable degree. The body starts to conserve salt at some point, but that’s about it. The old maxim “ration your sweat, not your water” is recognition of this.
Eating food is important as well. That’s the “electrolyte” part they are talking about. Empty stomach means the water just runs through, along with electrolytes.