In RapidAPI you can set a cookie for a particular domain that will be sent in all the requests to this domain.

Choose a session and open the cookie window

Go to Sessions in the top left corner. Choose a session or create a new one, then click Manage.

Add a new cookie to the session

Click on the plus button to add a cookie. Set the name, value, and domain for your cookie.

Build your request and check the HTTP message

If the domain for your cookie is set correctly you will see the Cookie header appear in the HTTP message below the request for this domain.