I know this is unimportant lol but it actually looks more like she had the bottle in her hand and when he tried forcing her into the car she tried to resist by using her arm to block from getting inside and she let go of the bottle in doing so. Her arm hits the car between sliding door and passenger door. Then the passenger tosses it out.
I'm guessing the video didn't show the plate clearly enough, otherwise one would think this case would be over by now. As a few have mentioned, hopefully the water bottle has some type of clue as to who they are and just waiting for results... though if she or they (if they got passenger prints too) are not already in some search database wouldn't it be back at square one?
I'm getting more and more concerned for her well being since this video has been on news. Hopefully someone will come forward soon as I'm sure he would easily be recognized by acquaintances, family, friends etc. He's a big guy, I know I don't know anyone that looks like that but if I did I'd surely remember him.