rest-api-orderby-meta-value.php

<?php 
/**
 * Check the orderby param for the particular REST API for hte custom post type. 
 * If it is set to a particular meta_ket, then set the orderby and meta_key query args/
 * @link https://www.timrosswebdevelopment.com/wordpress-rest-api-order-by-meta_value/
 */
function filter_rest_accommodation_query($query_vars, $request) {
    $orderby = $request->get_param('orderby');
    if (isset($orderby) && $orderby === 'number_of_beds') {
        $query_vars["orderby"] = "meta_value_num";
        $query_vars["meta_key"] = "number_of_beds";
    }
    return $query_vars;
}

// The filter is named rest_{post_type}_query. So you need to hook a new filter for each 
// of the custom post types you need to sort.
add_filter( 'rest_accommodation_query', 'filter_rest_accommodation_query', 10, 2);
?>