If the results obtained from the breathalyser test exceed 0.25 milligrams per litre (0.15 for professional drivers and drivers with less than two year's driving experience), the driver will receive a €500 fine.
Should the test register an amount above 0.5 milligrams (0.3 for professionals and inexperienced drivers) or if the driver has been fined for the same reason in the previous 12 months, the fine doubles to €1,000. The driver will also lose their driving license for a specified period of time.
Criminal charges for driving while under the influence of alcohol in Spain will be pressed against any driver with a blood-alcohol level in excess of 0.60 milligrams per litre, as measured in a breathalyser test. A criminal offence may also be committed if the driver’s faculties are clearly affected by the ingestion of alcohol or drugs affecting the driver's ability to drive - even where the measured rate is below 0.60 milligrams per litre, or indeed if the driver refuses to take a breathalyser test.
The penalties will depend upon the circumstances of the case, if anyone was injured or killed, if damage was done to property, if it is not a first offence etc
There will certainly be a fine and removal of your driving license as well, potentially, as a community service order or a prison term. You will also have a criminal record.
Do not refuse to take a breathalyser test. To do so is an independent criminal offence, for which you will be charged, in addition to the prior offence of driving while under the influence of alcohol or drugs.