Add Product Expiration Date To Order Emails Full Tutorial https://wpsites.net/product/woocommerce/add-expiration-date-to-order-emails/

functions.php

add_action('woocommerce_email_order_details', 'add_custom_fields_to_order_email', 10, 4);
function add_custom_fields_to_order_email($order, $sent_to_admin, $plain_text, $email) {

    foreach ($order->get_items() as $item_id => $item) {
    
        $product_id = $item->get_product_id();

         $expiration_date = get_post_meta($product_id, '_expiration_date', true);

        if ( ! empty( $expiration_date ) ) {
        
            $expiration_date = get_post_meta($product_id, '_expiration_date', true);
            
            $date_of_purchase = $order->get_date_created()->date('Y-m-d'); /
            
            $product_name = $item->get_name();

            echo '<p><strong>Product Name:</strong> ' . esc_html($product_name) . '</p>';
            echo '<p><strong>Date of Purchase:</strong> ' . esc_html($date_of_purchase) . '</p>';
            echo '<p><strong>Expiration Date:</strong> ' . esc_html($expiration_date) . '</p>';
        }
    }
}