“Get the same product (any product) for free on any purchase" coupon code in WooCommerce

I need to create a coupon code that grants the same product purchased for free. Therefore when user purchases a product (not a specific product, any product) then applies the coupon code, he/she gets the same product for free: quantity goes from 1 to 2 for the same price.

I've seen solutions to achieve this with a specific product, but not with any product. Any suggestion?

via Chebli Mohamed