I wanted to send some coins to my friends in Tiny Tower, am I able to do so? If so how?
According to the Tiny Tower Wiki (Google cache), when you gift stock to a friend that are not able to stock the item you sent at a store, the game will send coins instead.
For example, California rolls are only for the sushi bar. If your friend does not have a sushi bar, and you send them California rolls, they won't receive the item, instead they'll get their worth in coins.