There is nothing you can do.

I've received several close variations of this email over the last few days:

Dear Professor,

I really wanted to get an A in your class.  I know the course is over, but is there anything that I can do to raise my grade?

What I want to reply is:

Dear Student,

No.

OR

Dear Student,

I really wanted you to get an A in my class, too.  If only you had turned in all of your work throughout the semester in a timely manner, that might have happened!

What I really write is:

Dear Student,

I do understand your desire to receive an A in my course.  However, the semester has finished, and there are no additional extra-credit activities or assignments to be completed beyond those that were offered throughout the 16 weeks of the course.  I do hope that although you did not receive the grade that you hoped for, you enjoyed the course, and that you have a restful break.

If only students were as eager to do work throughout the semester as they are when the semester is finished and there is no work to do.