Only with coupon code

@cocoamedia
We don’t have that option, and it wouldn’t be easy to implement.

But without our plugin, you could use something like this, combine/mix has_discount and add_to_cart:

if (WC()->cart->has_discount('COUPONHERE')) {
   // cart has coupon COUPONHERE applied
       if ( ! WC()->cart->is_empty() ) {
          return;
	}
	WC()->cart->add_to_cart( 54, 1 );
}

54 = productID

Resources:
Automatically add product to cart on visit
Programatically Add Products to your WooCommerce Cart