There are cars and there are cars at bars. After all, most bars have parking lots. Most patrons of bars imbibe. Police who need to increase their arrests for the month could do so easily by sitting outside of a bar and waiting for those who think they are perfectly capable of getting home, and take them on a detour to a holding cell beforehand. Do officers do that? Some might, but many rely on specific tells that give them reason to suspect a driver is impaired.
If you are in a situation where you are being tested for alcohol consumption and impairment by law enforcement, you may be going through an internal debate about whether or not to contest the blood alcohol test. You should be wary of the reason you give for denying a test. If you say you don't like needles, they can have you blow. If you tell them you don't want to blow because you hear the tests are unreliable, they can request a urine, saliva or hair follicle test.
So, while breath tests and blood tests are the most commonly used means of screening for alcohol in the blood, breath tests are far more likely because they are less invasive. Blood tests are more commonly used following an accident or in a situation where the suspect refuses to blow.
The good news is that if you have already taken a breath test and have failed, you know that they can be unreliable and that they've been thrown out of cases before. If you need help and are dealing with the fallout from a drunk driving arrest, a Florida criminal defense attorney may be able to guide you and build up a strong defense against your charges.