SERIOUSLY. WHY was it ALWAYS the throat with Sam? Was there some kind of competition going on between all the monsters and demons that he didn't know about? They 'hey, let's see who can strangle Sam Winchester to death' contest? There had to be. Why else would he constantly find himself struggling under an extremely painful death grip? Air supply cutting off, Sam struggled under the demon's hold. He could have shot the demon -- he should have shot the demon -- but Sam couldn't. The Doctor was someone that he'd spoken with before. He wasn't a bad person.
He couldn't kill him.
It was pointless trying to pull out the bottle of holy water that he'd stowed away in his jacket if he couldn't properly unscrew the cap. So Sam brought his arm up to grip at the hand that was holding to Sam's wrist and tried to pry it away from his arm so that he could actually get the damned demon off of him. Demons were much stronger than the average being though, so that had been pretty pointless as well.
The corners of his vision began to fade. Sam then screwed his eyes shut and, in that moment, he began to focus on breaking away from the demon by other other means. An invisible force pried it's way between the pair and, with a strength that Sam didn't physically possess, it shoved them away from one another. Sam toppled onto the pavement behind him and rolled onto his back, gasping for breath as his eyes took in the dark sky that hung above him. The gun clattered onto the ground beside him, but Sam quickly opted to dig into his jacket instead. Bringing out the bottle of holy water that he had been trying to grasp onto before, he popped the cap open and scrambled back onto his feet.
Then he hurled the holy water at the demon, knowing that as soon as it hit his skin he would burn.