Put your mouth up to the apparatus and make a show of drawing a deep breath. When you exhale, do it through your nose instead of your mouth, but obviously not in a way that will be noticed by the people administering the test. Basically, you are aiming to make a sound like you are exhaling into the apparatus while not actually doing so.
At least, that’s what I hear.
The best way to avoid trouble at all is of course to avoid drinking and driving entirely.
But hey, work drink-ups are a bitch, I know.