Just a stupid idea...
How to use your fridge as a whiteboard
First, get a fridge, then, get a whiteboard marker
Find a hidden spot and write something, then try to erase it immediately
If it didn't work, get another fridge
Otherwise, write again in the hidden spot, but don't erase it yet, wait a couple of hours, then erase it
If it worked, congratulations, your fridge can be used as a whiteboard
Write on it with the marker, as I am doing (doodle)
Optionally, you can buy some cool magnets (like these)
Glue a couple to your marker (add a protection so they don't scratch the fridge (if you care enough)
So you can leave the marker right on the fridge, ready to be used
Enjoy your fridge, bye =)