I've been carrying around a hydrojug 64oz 'keg' as I like to call it for a few years now. I don't always get through it every day during work hours (which is the goal), and it makes a show-stoppingly loud noise when I drop it, but it's helped me a lot and keeps me on track. When I don't get through it, I definitely notice that my mood, sleep, etc are affected. I keep it nearby during all procedures and bring it with me to our field stuff.
When I was in ER, I used to, sort of by accident/unintentionally, go the entire 12-15+ hour shift with one terrible junky meal courtesy of Uber Eats and a paltry amount of fluid intake. I'm talking a shockingly low volume for that length of time. The only 'exception' is if I ordered a diet coke, and of course that got sucked down instantly although it doesn't count as fluid intake in my book. I felt like **** 24/7 and could not bounce back from my shifts on my weekend. The literal definition of a work hangover. It was irresponsible of me to be seeing patients like that honestly, I'm really lucky nothing serious came of it. Now that I make a point to stay reasonably hydrated, I can actually feel my brain power decline when I get behind on my water. Truly idk how I was functioning on ER with probably 16oz of water or less every 24 hours, but it was stupid and I probably could have performed even better (and more importantly, felt better!) if I prioritized staying hydrated.
I know we often give you advice on here that you may not take seriously, but not going to the bathroom or eating/drinking enough is not a badge of honor and will absolutely be showing in your performance. Being hungry or dehydrated will absolutely lead you to make poor decisions, impact your ability to learn, and put yourself/others/patients at risk for harm.
Also, your management will never notice the fact that you are voluntarily doing this, it will never be 'Wow TechP, we notice you never drink or eat or use the bathroom, that's really impressive and proves you work harder.' Who cares that your coworker orders food or does whatever (except eating fat from a patient? That's concerning....). Focus on yourself, your role at the job, and learning as much as you can. And focus on taking care of yourself/building those good habits now. It gets harder once you have real-world/real-job responsibilities.
ETA: Also, not me chugging my water right at this moment because this conversation made me realize I was falling behind lol