infinite zest This isn't very uncommon. Lots of people stopped for DUIIs just assume they're going to get busted so they drink as much as they can quickly so they can be drunk in the drunk tank overnight. Coke's a little different, since it's hard to tell the difference between someone who's had too much caffeine and high on coke apart, but dude was probably figuring the cop would know and geeked while he could.
Konversekid Clearly chugging a bunch of alcohol during a stop can also create a defense case against a DUI. I've had a lawyer friend say that it makes it difficult to prove that you were drunk while driving if you do this, and you basically should just say that you were nervous about the stop or something of that nature.
infinite zest Interesting. But how quickly does that register in a breathalyzer test? Like, if I took a shot of whisky I wouldn't feel the effects for a minute or two, because it's not in my system yet, it's just working its way around. Also, I remember summers at the beach where the cops would give out DUIIs to folks who were visibly intoxicated but hadn't even stepped into their vehicles yet.
Discordia I have a friend who keeps a bottle of whiskey under his seat for this purpose. He says if he's ever pulled over for a DUI he'll hop out of the car throw his keys in the trees (important point not to be holding the keys) rip open the whiskey and chug it down. So at car he can say on being pulled over he was distraught and chugged the whiskey to calm his nerves.
Maybe it'll work. Maybe it won't. But best idea is just don't drive drunk. I mean if you have that convoluted of a plan then you have drinking problem. He should be more worried about driving off a cliff on Hwy 1 as he lives in Mendocino.