In real life, to wash your hands, you must put your hands in the Washbasin, turn on the faucet, ( hot or cold ), then grab a towel and clean the water off the hands. However, in a LITERAL water world, is it really necessary to "wash" your hands? I mean, Bojack is in water arleady, so his hands can't get dirty from anything as the water arleady cleans them. If anything, the Vodka would have only made a nasty smell and there isn't even a Washbasin in the world.