// add item to cart on visit
add_action( 'template_redirect', 'add_product_to_cart' );
function add_product_to_cart() {
    if ( ! is_admin() ) {
        $product_ids = [385, 386];

        //check if product already in cart
        if ( sizeof( WC()->cart->get_cart() ) > 0 ) {

            foreach ( WC()->cart->get_cart() as $cart_item_key => $values ) {
                unset( $product_ids[array_search( $_product->id, $product_ids )] );
            }

        }

        if ( count($product_ids) > 0 ) {
            foreach($product_ids as $i => $$product_id) {
                WC()->cart->add_to_cart( $product_id );
            }
        }
    }
}