Each day that you check in with the game you will have an opportunity to spin a wheel to win a free prize. Einar Davidson and his Lucky Spin on wheels appears each day, from midnight in your time zone, until the wheel is spun. The prizes are either coins, free lives, or a power up. These bonuses can all be saved until you need them.
The video below is a detailed explanation on how you can collect your daily bonus via the Lucky Spin.