"through the cracks of sleep" is a wonderful line! :-)
Terrific haiku showing the strengths of the genre as a single line of poetry and still remaining a poem filled with tension and resonance.
Unless a danger noise occurs, I can sleep through anything including the most violent of thunder storms. I've written a few poems about sleep, who hasn't, but the above one is wonderful, and I'd just like to add one of mine here…
curling up at dusk
the park bench sleeper
turns over a new page
1st Prize, Fellowship of Australian Writers, Queensland, International Haiku Contest (1996)