I have seen "manger/boire en suisse" listed as an idiom to mean to eat/drink alone.
Is "manger/boire en suisse" an idiom that is still in use today?
Could this idiom also be mistaken to mean: eat/drink in Swiss?
It's quite an old expression and is seldom used nowadays. It comes from a cultural difference: When among friends in public places (bar, pub...) the French often, in turn, "paie la tournée" - pay a round. When in the Germanic cultures each pay for his own drinks as a more general rule.
The expression is still in use!
I mean for adult people, who speak some educated language versus some common one, and is the equivalent to say: 'Boire en juif', thus, it's no more well sawn to make reference indeed to jewish supposed attitude:(!