Hi @Danavir ,
yes you can send him a free product and to implement that you can create a discount coupon with 100% discount just for him which can be redeemed only once and let him order the product again and send him the discount coupon code beforehand, so that he can redeem it at checkout at 0 price.
You can learn more about discounts from the doc below https://help.shopify.com/en/manual/discounts . Also do let me know if you are stuck anywhere in implementing what I told you
Thanks