It could make you tired if you did it couple times before bed so I say it does help you sleep. Plus your mind is probably still full of perverted thoughts, so you have something nice to dream about.
Sometimes when I try to sleep, I just couldn't because the all the energy in my body has transferred to my analog stick and just couldn't sleep. By Fapping and releasing the energy(cum), I could fall asleep. So I say it is a good sleeping pill.
If I fap before bed, it makes me dead tired, but only if I don't move after the deed is done. That even means that I can't clean up the aftermath, if I do, I stay awake.