To be wank drunk is a sensation solely associated with males who bash one out and suddenly succumb to the sensation of feeling lethargic and sleepy, almost drunk like immediately following a cheeky tug. Whilst males feel knocked out after having shot their loads, the expression wank drunk can also refer to general groginess and lethargy during periods of inactivity and boredom, as if they have just had a tug, are spaced out, and feel like just sleeping.
Alright mate, you look really tired.
Yeah, I'm fucked. I feel wank drunk.