A respected neuroscientist, Andrew Hubberman I think is his name. He said that there are only a few things that IMPROVE your quality of sleep, many things that will help you fall asleep, but those usually decrease the quality of your sleep.
So a few of those are mildly sedating, but if you just want to zonk out, take 50-75mg of dipenhydramine(sp?). That'll knock most people right out. Just dont go 100mg or above, it is a deliriant. You don't want to go into delirium, trust me.
It does not improve your quality of sleep though. And you shouldn't do it that often, especially if you're older, there's a hard link between constant use and Alzheimer's or dementia.