I don't think there is actually a straightforward definition of this. I'll just go ahead and tell you what I think it means. Sleep hacks are just methods, that are unconventional or unknown, to help improve the quality or value of your sleep.
I use the terms quality and value because a lot of the hacks I'm going to show to may value you in some other ways rather than sleep. I, like a lot of other people, want to sleep less, so we have more time each day. Obviously, if you're looking to sleep a full 9hrs, without interruption, we're going after two different types of quality and value.
28 Hour Day - The 28 Hour day is a very interesting type of hack for your sleep. You follow a 28 hour clock and adjust your sleeping patterns to that. It turns a 7 day week into 6.
Sleep Log - Sleep logs are very powerful tools to help you tweak your sleep. Write down your sleeping patterns for a period of time and you can learn a lot.
Eating For Sleep - Eating is an important part of sleeping. If you eat the wrong foods, you're not going to get the best possible sleep. If you're looking to reduce the hours of sleep you do, than read this.
Eat to Sleep Better - More eating tips that are going to transform the way you end up sleeping - for the better.
Cortisol Sleep Issues - Cortisol is a stress hormone that can lower your sleep quality. Learn how you can lower the cortisol levels and get a good night of sleep.
Napping Tips - Napping is an excellent way to get a little more productivity out of your head. It often works as a great refresher for your day.
Sleeping On A Plane - It is tought to sleep while you're on a plane. I have a few methods that should help you make this easier.
Baths For Sleep - Taking a bath to get some sleep can really work. There are a few different types of baths you can try.
Write Down Invading Thoughts - Thoughts have a way of getting your mind going and it can keep you up all night.