Festival of Hearts has two types of rewards.
The first one is a reward for competition. Those players who will get the biggest amount of hearts faster than the others will get this reward. It has coins, experience, recipe cards and prize cups inside.
Also you can get rewards from your current festival chest. To do so you need to get a certain amount of hearts during the festival. Complete orders with upgraded recipes at the tavern to get hearts. Inside you will find: coins, experience, recipe cards, diamonds and festival crowns that shows your participation status.