I don't think that the sake scene was at all unrealistic.
A majority of people try drinking at least once, I thought that
Ranma and Akane would have probably try it together. And anyway,
MI had a lot of drinking in it, so it's not something Rumiko
would never write about.

I think the first time or so Ranma really drunk was when he went
in that onsen race, and ended up in the bathtub of hot sake, with
Shampoo... Neither of them can hold their sake. (Though turning
Ranma from a guy to a girl did sober him up, properly!)

Kun-chan...