Elsabe

@pipdig it needs to still display the product name so this would be a better solution:

foreach ($order->get_items() as $item) {

    $product = wc_get_product($item->get_product_id());

    $sku_markup = '';
    if ($product) {
        $sku = $product->get_sku();

        if ($sku) {
            $sku_markup = ' ('.esc_html($sku).')';
        }
    }

    $output .= absint($item['quantity']).' &times; '.esc_html($item['name']).$sku_markup.'<br />';

}

Awesome thank you!