Dear boy at the water container.

Dear boy at the water container,

Thank you for pouring me a cup of water at lunch.  I don't know what your name is, but when I thanked you, you said "My pleasure."  Two days later, you did it again.  "My pleasure," you replied once again when I thanked you.  I've never spoken to you and I can't even honestly remember what you look like, but I really appreciate your genuine kindness.

Hopefully your future friend,
Sara