Christine-
I would think that studying the night before might help, but drunks are unscrupulous, inscrutable, or just not trustworthy. They would probably cheat.
You are not looking for a slam dunk here. You just need to demonstrate his uncooperative behavior.
Alcohol has a fairly short half-life, so the test needs to be administered during the time of impairment.
There are several alcohol tests that are available OTC. Get one and a witness. He will refuse, but once you have several documented cases of his refusal, you will have strong standing in the court.
JayR