When I explore sleepiness through the sense fields, and bring attention to the sensation part of it, it is no longer sleepiness or drowsiness or dullness. It is just a set of sensations, and parallel with it, a set of thoughts.
Together, they make up the appearance of sleepiness, and when attention is brought to the sensation aspect of it, it is revealed as something else. And I also notice how awareness itself is never sleepy or drowsy or dull or anything else. It is always and already clear and awake.
The thought aspect of sleepiness is still a little unclear to me, but there is a slow downward movement there, like a thick sticky fluid. And when it combines with the sensation aspects, the gestalt created is sensations with a slow viscous downward movement, which appears as sleepiness.
When this is seen, the gestalt of sleepiness falls into its components of sensations and thoughts, which may make the sleepiness go >poof<. Unless the movement is too strong, in which case it brings sleep. And awareness is either aware of itself through that process, or not.