So, you've mastered the words and, feeling confident, you stroll into a bar and order half a litre of beer or (worse still) a pint. The barman stares back at you like you're from Mars. You can't understand what you did wrong because you really practised this one. The fact is that you have just trodden on the first of many (purely cultural) banana skins. If it's any consolation a, Spanish person would make the same mistake in Britain!
Size IS Important!
The odd thing is that beer isn't sold by quantity in Spain and so ordering amount of it doesn't make any sense. Beer is sold solely on the type of glass that it is served in. A caña is quite often a large wine glass of beer and many rural bars don't have large glasses …but let's take a tour around the extra minefield of bar glasses. Although the word for a 'pint' does translate into Spanish as 'pinta' (pronounced PEEN-ta), this same word is in more common use as meaning 'speckled' or 'spotted' and may come across as you wanting 'spotted beer.'
Bigger??
Your host may offer a smaller glass from the shelves behind the bar when larger ones are clearly available …reinforcing your wish for something that holds more beer may be required. Outside of communities that have a lot of British people, the act of consuming appreciable amounts of beer is largely unknown and thus you are fighting a two-pronged battle with a language and a culture.
Your glasses!
Copa (pronounce the 'o' as in 'orange') …a wine glass
Tubo (pronounced TOO-bo) …a long slender tubular glass (holds about a third of a litre)
Tanque (pronounced TAN-kay) …not available in every bar and the size and type can vary. The smallest of these holds about half a pint. Obtaining a pint-size 'tanque' may require the addition of the word 'grande' (pronounced 'GRRAN-day).