Cure for Insomnia
For a hunter living life on the road, sleep was hard to come by. In between driving, researching, following leads, digging up graves and fighting monsters there was little enough time for recreational activities (usually involving bars and women), let alone for catching a few zzzs. Dean was used to only getting a few hours of sleep every couple of nights, and he could function on less if he had to.
But every so often, Dean suffered from insomnia. He would be on the go for 48 hours straight, finally have the chance to collapse into bed utterly exhausted, and then wind up tossing and turning all night, unable to fall asleep. Sometimes it was caused by an adrenaline high, sometimes by stress or worry, sometimes by restless memories, sometimes by nightmares. Whatever the origin, it left Dean dangerously fatigued. In his line of work, he couldn't afford the dulled senses, slow reflexes and impaired judgement that resulted from sleep deprivation. If allowed to persist it could get him killed.
Of course, Dean would never agree to go to a sleep clinic no matter how bad it got. He was stubborn that way.
In the end, it was Sam who came up with the only remedy that worked.
Whenever Sam noticed that Dean wasn't sleeping he would bundle his brother into one of his own hoodies, take the keys to the Impala, tuck Dean into the passenger side of the car and drive. They would leave the lights and the noise of populated areas far behind, taking to the back roads and deserted highways, driving with no particular destination in mind. Quietly, Sam would begin to sing.
Lulled by the soft roar of the Impala's engine and the sound of his brother's voice, Dean would fall fast asleep. He wouldn't wake until eight hours later, when Sam finally pulled back into the motel parking lot and gently roused him.
Dean never got a better night's sleep.