It seems not possible to forward custom Guzzle options to the handler about guzzle-oauth2-subscriber HOT 1 CLOSED

// Authorization client - this is used to request OAuth access tokens
$reauth_client = new GuzzleHttp\Client([
    // Disable SSL verification
    'verify' => false,
]);
$reauth_config = [
    // ...
];
$grant_type = new ClientCredentials($reauth_client, $reauth_config);
$oauth = new OAuth2Subscriber($grant_type);