Very colloquial: dos por uno
Hi again, here we have a very used expression in Spanish for the well known: "Happy hour" in English.
By the way , I have only just read that this has been forbidden by the Catalonian government.
Adiós a los felices "2x1" en los bares.
"Happy Hour" was banned here in Massachusetts several years ago. The thought was that people were getting too drunk and then driving home.
We say that in the USA also. "Two for one well drinks" is a very common special for our happy hours.
"Well drinks" are cocktails made "from the well"... i.e. using the cheaper house brands of liquors.