oliver_get_bookings_for_tomorrow.php

<?php
/**
 * Get all bookings scheduled for tomorrow
 */
function oliver_get_bookings_for_tomorrow() {

	// Get tomorrow's date
	$tomorrow = date( 'Y-m-j', strtotime('tomorrow') );

	$args = array(
		'post_type'				=> 'bfwc_booking',
		'posts_per_page'	=> -1,
		'meta_query' 			=> array(
			'relation'			=> 'AND',
      array(
        'key'     => 'bfwc_start_date',
        'value'   => $tomorrow,
        'compare' => '='
      ),
			array(
        'key'     => 'bfwc_status',
        'value'   => 'cancelled',
        'compare' => '!='
      )
    ),
		'fields'			=> 'ids'
	);
	$bookings = new WP_Query( $args );

	// A list of bookings for tomorrow
	$booking_ids = $bookings->posts;
	if( $booking_ids ) {
		foreach( $booking_ids as $booking_id ) {
			oliver_send_reminder_email( $booking_id );
		}
	}
	wp_reset_postdata();

}
add_action( 'woocommerce_scheduled_sales', 'oliver_get_bookings_for_tomorrow' );

/**
 * This function sends the email
 * Check the booking ID for the booking product
 * Then send an email accordingly
 */
function oliver_send_reminder_email( $booking_id ) {

	$booking_product_id = get_post_meta( $booking_id, 'bfwc_product_id', true );

	// Make a list of Booking Product IDs and Keycodes
	// Use this pattern: $booking_product_id => $keycode
	$keys = array(
		'914'	=> '1234', // E.g. 904 is your booking product ID, 1234 is the keycode for this product
		'923'	=> '5678'
	);

	// Find the keycode
	$keycode = isset( $keys[$booking_id] ) ? $keys[$booking_id] : false;

	if( $keycode ) {

		$to = get_post_meta( $booking_id, 'bfwc_user_email', true );

		$subject = __( 'Your key', 'bfwc' );

		ob_start();

		wc_get_template( 'emails/email-header.php', array( 'email_heading' => $subject ) );

		$content = ob_get_clean();

		$message = sprintf(
			'<p>%s<p>',
			sprintf(
				__( 'Your keycode is %s', 'wcmo' ),
				$keycode
			)
		);

		$message = apply_filters( 'bfwc_reminder_email_content', $message, $booking_id );

		$content .= $message;

		ob_start();

		wc_get_template( 'emails/email-footer.php' );

		$content .= ob_get_clean();

		wc_mail( $to, $subject, $content );

	}

}