Being able to show a source is always the best! people will trust you more that way too and you can even prove that you informed yourself and didn't just copy something :)
But finding something on this matter will be hard since noone ever made any studies on this. Which I can understand since it would not only cost alot of money to pay all the subjects involved in the experiments, but even for short term effects of e.g. drinking while standing vs. drinking while sitting you would need >500 for both parts and them trying it for like halv a year to a year. And thats only for short term effects, noones gonna pay to find out the long term ones, at least I wouldn't waste money for that...
It's just a cultural and religious thing to not drink while standing, some people for some reason made up some "hypothesis", if you can it that, and those spread around, leading to people believe that drinking while standing is bad. For some reason they didn't put any effort into making up some arguments for them though...