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.

“Manger/boire en suisse” refers to the Vatican Swiss Guards who had to eat/drink standing (alone) while on their watch guard. – Hussein FAKHRY