Answer:
Dear (name of friend),
How are you? I hope you are doing fine. I am writing this letter to apologise about the fact that I spilled water on your project work. I know how much effort you have put into this project, even if you didn't too much or did much, I want to tell you how sorry I am. I hope you will forgive me for what I did and I won't do it again.
Cheers,
(Your name)
I don't know if this is for an assignment or anything, but here's my response. :-)
