Well that's disappointing to hear about Nuun/Nestle.
So one of the podcasts my PT recommended is "The Real Science of Sport" and it's hosted by some South African guys, one of which has a PhD in something something to do with sports. ANYWAY. They're really great, nerdy listens, usually over an hour long, AND they did a few episodes specifically on hydrating and fueling for endurance events.
On one of the episodes they were talking about your body and it's desire to keep your water/sodium levels balanced, and how sports drinks and things like salt caps work with that (and about "drink to thirst" and what science says about that.) If I'm remembering correctly, the gist was that if you've taking in MORE sodium than your body needs to keep balanced levels, you will want to drink more water....like your body will just crave it. And if you HAVEN'T taken on enough sodium (and have sweat a lot of it out) you will crave salty things, OR your body will try to get rid of water (to balance with the reduced sodium level) by making you pee. There's obviously more to it than that, but if I'm remembering correctly, that was the basics.