//APPLY COUPON AUTOMATICALLY IF PRODUCT ID IS IN THE CART
add_action( 'woocommerce_before_cart', 'wpninja_apply_matched_coupons' );
function wpninja_apply_matched_coupons() {
$coupon_code = 'sapikupon';
if ( WC()->cart->has_discount( $coupon_code ) ) return;
foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
// this is your product ID
$autocoupon = array( 1035 );
if( in_array( $cart_item['product_id'], $autocoupon ) ) {
WC()->cart->add_discount( $coupon_code );
wc_print_notices();
}
}
}