What is the hydration/ energy in this game?!?!

I spawn in on customs as a pistol scav. I run into a couple of guys and barely manage to take them out. I have like 4 blacked limbs and everything is hurting but I'm alive. I luckily spawned with an adrenaline shot so I popped that and started looting the guys. I got their heals and fixed myself up as best I could.

Then I start making my way but I notice my hydration is at 5. I'm thinking, "hmm, maybe I should drink this full apple juice in my bag" that I got off of one of the players, so I do.

I keep slowly trekking to extract as I am more juiced now than I have been in a long time. I notice the hydration indicator has a -2.00 next to it so I assumed it would run out at 2 a minute. Seeing as how I had 40 hydration after drinking the juice, I felt I would have plenty of time to make it to extract as long as I don't run into anyone. But then about 45 seconds later, to my surprise, my guy falls over dead due to exhaustion or whatever.

I'm pissed.