просто читаем куки

func readCookies(){
        
        if let cookies = HTTPCookieStorage.shared.cookies {
            for cookie in cookies {
                print("\n\n\(cookie)\n\n")
            }
        }
    }

ставим куки к запросу

...
 let request =  NSMutableURLRequest(url: url! as URL)
 let cookies = HTTPCookieStorage.shared.cookies
        for cookie in cookies! {
             request.setValue(cookie.value, forHTTPHeaderField: cookie.name)
        }
 webView.delegate = self
 webView.loadRequest(request as URLRequest)