Get all drunked-up, and have a friend administer the tests to you. Repeat until you can master the tasks, even when on a full-blown bender.
Or better yet, stay off the roads when you're buzzed. Hey! What a wonderful idea!
My father was pulled over one time and administered a roadside impairment test. The test began with the officer asking him to say the alphabet backwards beginning from W, without pausing, start now. No joke. I am stone cold sober and could not do this if you paid me.