Glad to know I'm not the only one who goes out and practices track stands a little tipsy. You get to be much more chill and fluid (which is just another way of saying sloppy).
Usually my biggest problem with a track stand is if I've been sprinting and have to come up short. I'm totally juiced and have to do a lot of little adjustments because my muscles are still very twitchy.
As for standing while seate (?), I find that it's useful to start out standing over the front axle where I'm strongest and then back onto the saddle, maintaining balance the whole way. I can do this one handed, too, so the drink should be safe.