Answer: I will not write this for you but I will give you a format.
Explanation:
Dear (insert friends name)
How are you, I’ve heard that you haven’t been feeling well recently. Here are som things that I do to help me stay healthy: (list some things you do, running, eating, ect.)
I hope these help you, sorry you don’t feel well
Your friend,
(Insert your name)
I hope this helps you.