The platform offers a built-in "Thanks" page to publicly recognize hackers who have helped you and your users with a security issue. Limited edition swag is often well-received, as are free coupons or vouchers for whatever services/products you offer. For hackers with the best contributions, considering offering to host them near your office for a lunch/drinks or cover their admission to conferences your team may be attending.
If you want to recognize a hacker with swag, you can use HackerOne’s built-in Swag feature. You will need to first make sure that swag is turned on by checking Settings > Swag. Once swag is turned on, the option will become available in each report under Set Award > Swag. HackerOne will automatically prompt the hacker to provide their address when you reward them swag; once they fill it in, you should ship their reward directly to the address provided.