Exos Heroes has an option to redeem coupon codes for free in-game items and currency!
Here’s a list of all active codes:
How to Redeem
Note: You can also just directly access the coupon form here.
Bring up the menu in the top right corner.
Tap on “Settings”.
Tap on “Input Coupon”.
Select “Global” from the drop down menu and enter your airship name and the coupon code in the relevant boxes.
The rewards will be sent to you by mail.