Austrians have quite the fun drinking culture.
Therefore it's very important to me that Roderich | Austria is both a lightweight and a heavy drinker, the best disastrously fun combination.
Consider those closest to him knows how much he can drink everyone under the fucking table.
And consider: he is the worst drunk to ever be in the company of.
Loud, volatile, aggressive — this is because alcohol essentially stripped down all those carefully arranged walls of prim, proper poise as expected of the once emblem of all things aristocratic, imperium, all that revering shit.
As a drunk, the former feral youth he once was would take the spotlight and shine like the beautiful gemstone of utter chaos and depravity.
He's terribly touchy too but not in a cute way—shoving, pushing, hitting whoever is within proximity. Then turned to clinging with a vice grip that would make you regret thinking this would be an endearing vulnerable moment.
Oh no, this princess for all his undaunting grace would give you grief over the smallest things he remembered about you especially if you had been his former spouse. Antonio was a prime target, was subjected to plenty which he adored anyhow, he enjoys seeing this unrestrained version of the Austrian.
The Germans would both be shocked and enjoy it the first time they witnessed this, only to be horrified at the umpteenth time the Austrian is drinking, then forcing those closest to him to take another shot, chug another glass, what have you.
This is why Roderich tries to keep drinking to a minimum, he knows how he gets when inebriated, and the hangover each time is quite the kicker. Though incomparable to the mortification of whatever tales others would share of his drunken exploitation.