In my experience the strongest over the counter sleeping pill that works best for me is Unisom sleep aids.
Tylenol PM and Simply Sleep are also good sleep aids that you can buy over the counter.
You can also drink cherry juice or eat some cherries as they naturally contain Melatonin which can help some people get to sleep when they have insomnia.
The cherries and cherry juice is also good for your health as well.
For some people over the counter sleeping pills may wear off and then the person may need to get prescription sleeping pills that are much stronger than over the counter sleeping medicines.
You can also buy Melatonin pills that help you sleep and you can buy sleep aids including the Melatonin online through ebay and other websites.