Beer coat

exp.

Heard in Dublin and Limerick

The invisible but warm coat worn when walking home after a booze. Cruise at 3 in the morning.

In use

By the time we walked 5 miles home from the pub, my beer coat had fallen off

Posh English

By the time we walked five miles home from the public house, my warming mantle bestowed by strong drink had worn off.

Same phrase, other counties