Ethanol inhibits the antidiuretic hormone (ADH) also known as vasopressin. ADH is used to regulate tonicity of bodily fluids, so essentially the amount of salts you have flowing through your body. If your body detects that you're running too high of a salt level, the pituitary releases it to tell the kidneys to reabsorb more water from the nephrons and put it back into circulation thus diluting the salts.
So, since ethanol inhibits the function of ADH, the kidneys just discard everything and beer has a lot of water.
I think the question was more about substituting the toilet with a fridge, than the details around how drinking beer mechanically turns to piss. Interesting read though!
You see, the thing is that we've got these things called bladders that store the waste fluids our body has so far filtered out so that we're not constantly dribbling a bit of piss and making it trivial for predators to track us. When that bladder gets full and stretches, it is detected by some nerves and then our brains signal that it's time to find a toilet or fridge to piss in.
Hopefully that relieves the pressure of your curiosity a bit.
IDK but I pissed in he closet once. I thought there was a urinal in there for some reason. It takes a lot of booze to get to this point. Literally, can't utter complete sentences, entire fifth of vodka kind of drunk, for you to reach the point where pissing anywhere other than a toilet sounds like a good idea.
Thankfully cleanup wasn't too bad the next day, cause my urine was so diluted that it didn't even smell like piss. Initially I thought that I spilled water.