Add custom field to order emails

functions.php

<?php
/**
 * Add the field to order emails
 **/
add_filter( 'woocommerce_email_order_meta_keys', 'some_order_meta_keys' );
 
function some_order_meta_keys() {
        if (get_post_meta( get_the_ID(), 'Some Field')) {
                echo 'This is the custom information you entered in Some Field: ' . get_post_meta( get_the_ID(), 'Some Field', true) . '<br />';
        }
}
?>