Option source function in advanced select

Hello,
I have a problem to get values in a checkbox-list. Already red some articles here and in the documentation (https://docs.metabox.io/fields/checkbox-list/#template-usage)

On the user side, I have this field:

[
    'name'              => 'Vehicles',
    'id'                => $prefix . 'vehicles',
    'type'              => 'text_list',
    'options'           => [
        'VW'    => 'Brand',
        'Golf'  => 'Name',
        'Black' => 'Color',
    ],
    'clone'             => true,
    'sort_clone'        => true,
    'clone_as_multiple' => true,
    'max_clone'         => 3,
],

How can I access those user specific values?
Tried it whit:

[
    'name'            => 'Select Vehicles',
    'id'              => $prefix . 'selected_vehicles',
    'type'            => 'select_advanced',
    'options'         => getVehicles(),
    'multiple'        => true,
    'select_all_none' => true,
],

...

function getVehicles() {
    $values = rwmb_meta( 'vehicles', ['object_type' => 'user'], $user->ID );
    foreach ( $values as $value ) {
        return $value;
    }
}

But nothing cames back... 🙁
I'dont have any other ideas. Thanks for supporting me!