Free Rewards
The Free Rewards system is a feature that allows players to earn in-game rewards by watching advertisements. This system was introduced to the game between patches 7.11 and 7.12. It is currently undergoing a testing phase and is only available for select users in North America and Europe.
The Free Rewards system can be accessed through a button labeled "Earn Free Rewards" above the news section on the right of the main menu. If you do not see this button you are either not currently eligible or have already viewed the daily allotted ads.
Functionality
On the Free Rewards menu, the player can click a button to watch a sponsored advertisement.
The player has a limited amount of ads that can be watched, which currently seems to be 2–6 per day.
Once the daily ad limit is met, the Free Rewards button will disappear from the main menu until the player is eligible to watch ads again.
The progress bar goes up to 50. Once completed, the bar will stay at 50 until another ad is watched, then it will reset and start counting again at 1. Thus, players are granted another opportunity to progress the track and earn more rewards.
Rewards
With each advertisement watched, the player earns 
10 or more coins, and the watch count progress bar moves up.
Once the player reaches 25 ads watched, they will open a Reward Chest, which contains an additional reward. This occurs again at 50 views with a Grand Chest.
Any of the following types of Store items can be earned from these chests:
While it's not currently known which specific items can be earned from the chests, higher values rewards like Skins can only be obtained from the Grand Chest.