wpdb and acf via wp rest api

I ended up using $wpdb for my custom tables and went with wp_query for my custom posts with ACF fields

    $q = new WP_Query(array(
        'post_type' => 'coupon',
        'post__in'  => $cids
    ));

    $coupons = array();
    while($q->have_posts()) : $q->the_post();
        $p = get_post();
        $f = get_fields();
        $m = array_merge((array)$p, (array)$f);
        array_push($coupons, $m);
    endwhile;

And that’s how the cookie crumbles.