There is no evidence that any medication affects CVSA outcomes in any way (let alone in a positive way). Consuming alcohol before a CVSA examination seems to me like a foolish thing to do.

CVSA lacks the methodological weaknesses that make effective polygraph countermeasures possible, but that is not to say that CVSA has any scientific basis whatsoever (it doesn't). Be that as it may, the "behavioral" countermeasures outlined for polygraph examinations in Chapter 4 of The Lie Behind the Lie Detector may be helpful in passing a CVSA "test."