Twitch Authorization Code is saved in Cookies

Optional Parameter Type Description
force_verify boolean Specifies whether the user should be re-prompted for authorization. If this is true, the user always is prompted to confirm authorization. This is useful to allow your users to switch Twitch accounts, since there is no way to log users out of the API. Default: false (a given user sees the authorization page for a given set of scopes only the first time through the sequence).

Set force_verify to true in your redirect to twitch