One thing is how you'd feel, another is survivability. https://en.wikipedia.org/wiki/Caffeine states that LD~50~ for oral caffeine ingestion in rats is 192ppm, and only estimates the value for humans. Wikipedia doesn't exactly state it but it's safe to assume that the surviving 50% of rats will definitely not have had a good time though.

But "36 red bulls" is how much? I can buy red bull in 0.25l and 0.5l cans in local stores, what is available in the US in unknown to me, so I'll assume equivalent can sizes. So between 9l and 18l of red bull over about 11hrs. IDK that sounds like a lot of fluid no matter what. Maybe the electrolytes in the red bull will prevent water intoxication, but he'd definitely have had to pee a lot. Perhaps his kidneys would have a hard time following along with the excess electrolytes, but enough to become hypertonic?

Anyway a liter of red bull contains 320mg of caffeine, and thus 9l is 2.88g and 18l is 5.76g. Assuming a 100kg human body that's 28.8-57.6ppm spread out over 11hrs.

Had the caffeine been ingested all at once, then he'd at worst have hit 30% of LD~50~. But given that the subject probably didn't ingest 18l of fluid instantly, because then the story would include that in the title, the consumption was spread out. Elimination half-life for caffeine is 3-7hrs, meaning that the initial caffeine could be reduced to 1/8 by the end.

I don't have the time to do the integral equations, but my best bet is that our subject plausibly could survive, but his kidneys, penis and psychiatric state could do with a check up.