I am going to ask that you read this completely before misunderstanding. I am not blaming you and you certainly should give him consequences but before you do, I'd like you to consider something.
I have a 20 yr old son and a 5 year old daughter (15 years and almost 2 months apart). Think about it, even if he wasn't tired, a 14 year old does not have the patience for a toddler/preschooler that an adult would have and NO ONE has patience for whiny (not even the parents). My point is, you can't expect him to actually be patient especially with whiny.
That said, he certainly can not be physically rough with her. In today's situation, clear instructions would have made a difference..."Can you move your backpack and put the seat up so she can get out?" would have prevented any misunderstandings. As it was, you said to "Help get her out of the car" only asks him to facilitate the outcome while not suggesting the route you want him to take to achieve the outcome. He did just that...but not as he should have and not as you wanted...but he did act like a 14 year old boy.
As for his punishment...what works for each child is different. What does he "have to have" his cell phone, the internet, the radio? Take that from him for whatever timeframe you decide is appropriate. Or have him volunteer w/ you at the church's nursery so he has to show patiences where he is supervised and you can lead by example.