The waterless lazy-man's shower. Basically getting up out of bed, and not showering with water, soap and shampoo.
Reference: In an early scene in the movie Braveheart (1995), the young William Wallace woke up out of his makeshift bed one morning, brushed his outer forearm against his face a few times, and was ready to start his day - no brushing of his teeth, no coming his hair, or anything remotely hygienic.
I'm late for class so I'm gonna have to hurry up. I'll just take a Braveheart shower and go.