This is one of those situations where "cool" might not have the same meaning internationally. The safest ways to use "mojosa" is to refer to trends and style. You can get away with using it as a synonym for "bonega" (but in which case, why not just say "bonega"?) However, to say that it's not kind of acceptable to drink another person's bear, you'd want another word like "afabla" or "akceptebla."
You might be able to use “Mi estas trinkanta lian bieron.” to emphasise that you were drinking it rather than doing something else with it.
I await confirmation or correction from experts on that one.
Is there an Esperanto word for quaffing? Quaffing is similar to drinking but you spill more (thanks Terry).