The short answer is: yes, they do work, however, to a certain degree.
Most ingredients that these supplement companies add in their formula have all been researched thoroughly by many researchers. They also have been used in traditional medicines for a very long time.
With combined research and anecdotal experience, we can say that these supplements will help you with getting asleep faster and more profound.
You have to understand that these supplements are (almost) all completely natural, which means that they will practically have no adverse effects as well.
A sleep medicine prescribed by your doctor will be much stronger and more effective. But, it will also be harder on your body in terms of side-effects and can be addictive.
Take melatonin, for example. It has over 20.000 studies on the physiological effects, but also safety.
If you are looking for a supplement that has sadetive effects and also has the ability to help you with deeper REM sleep, than yes a bodybuilding sleep aid is perfect for you.