Try going to bed and reading or doing a crossword if thats your thing. Relax, get warm, engage the brain and tire your mind out.

Helps if you've exercised that evening too.

Do you drink lots of caffeine or any other type of stimulant throughout the day? You might need to look for the cause, rather than the cure?

Also, after your 5 hours do you still feel tired or are you refreshed and alert? Some people can get by on less sleep than others, maybe you are one of those?