You definitely make a fair point in regards to YouTube salaries, however he's a good looking guy who has quite a knack for actual content creation. I see him quite easily transitioning into more daily vlogging type content which has been a staple of YouTube for a while, and which, unlike running content, actually makes a few $$$
Moreover, social influence goes beyond YouTube. Your average motivational hobbyjogger can make a decent wage off their 10k instagram followers plugging fitness products. Ryan's currently on 13k off 5 months of content and has 4 years to grow: once you hit that first 5k or so on instagram, you start to get your content featured on people's discover page and growth goes further and further through the roof, so if he keeps working on it consistently, I don't see a reason why he doesn't hit 100k followers by the time he graduates, in which he'll be a marketers wet dream.
Mind you this should all be supplementary income. As far as I know he's majoring in Economics so it's not like he'll be completely short of a job once college is over!
Essentially, what I'm trying to argue is that the doors that will open as a result of growing his social media over time are far more plentiful than the amount that will open as a result of selling bottles-especially since he won't be able to market them properly!