Here's his account from a 1994 Vanity Fair:
"At a bar at the top of a ski lift at Aspen, Colorado, I was denied a gin and tonic because, 'at this altitude, it would be twice as strong.' Hot dog, bring it over."
And here's another version of the same incident which ran in the AP's obit:
Hitchens was an old-fashioned sensualist who abstained from clean living as if it were just another kind of church. In 2005, he would recall a trip to Aspen, Colo., and a brief encounter after stepping off a ski lift.
"I was met by immaculate specimens of young American womanhood, holding silver trays and flashing perfect dentition," he wrote. "What would I like? I thought a gin and tonic would meet the case. 'Sir, that would be inappropriate.' In what respect? 'At this altitude gin would be very much more toxic than at ground level.' In that case, I said, make it a double."
In his memoir, Hitch-22, Hitchens offered this drinking advice:
Of course, watching the clock for the start time is probably a bad sign, but here are some simple pieces of advice for the young. Don't drink on an empty stomach: The main point of the refreshment is the enhancement of food. Don't drink if you have the blues: It's a junk cure. Drink when you are in a good mood. Cheap booze is a false economy. It's not true that you shouldn't drink alone: These can be the happiest glasses you ever drain. Hangovers are another bad sign, and you should not expect to be believed if you take refuge in saying you can't properly remember last night. (If you really don't remember, that's an even worse sign.) Avoid all narcotics: These make you more boring rather than less and are not designed -- as are the grape and the grain -- to enliven company. Be careful about upgrading too far to single-malt Scotch: When you are voyaging in rough countries, it won't be easily available. Never even think about driving a car if you have taken a drop.
We'll drink to that -- and to Hitchens himself, a great writer and raconteur.