I recently completed Find Mii on my 3DS and unlocked Find Mii 2. When I started battling, I saw a new option that said "potion". I don't know what they are supposed to do. Are they used to heal a Mii or something?
There are different potions you can buy, and they each do different things, and cost a different number of Play Coins to buy and use.
The potions are:
Some important things to remember: Sometimes you will buy a potion, and it will not do anything. Also, when you buy a potion, make sure you have a Mii behind the one purchasing the potion who will then use it. If you buy a potion and there are no more Miis waiting to fight, you will waste the potion.