Sidra/Cidar

So we're in Asturias, Spain. Their main drink here is cidar.
It's a natural cidar that rarely costs more than 2 € a litre. They serve it in big glasses.
Tonight a woman goes from table to table pouring a few centimeters into the glass and handing it directly to you to drink. Many pour the dregs of the glass onto the floor.
The bottle is held high and the glass low, and the cidar somehow gets into the glass.
Some places have a little pump so you can pour the cidar when you want to. It funny.