PHP

Append a text string to WooCommerce single product title

remove_action( 'woocommerce_single_product_summary', 'woocommerce_template_single_title', 5 );

function woocommerce_template_single_title_custom(){
    $additional_text = ' More Info';
    the_title( '<h3 class="product_title entry-title">', $additional_text.'</h3>' );
}
add_action( 'woocommerce_single_product_summary', 'woocommerce_template_single_title_custom', 5);

Append a text string to WooCommerce product title loop

remove_action( 'woocommerce_shop_loop_item_title','woocommerce_template_loop_product_title', 10 );
function change_product_title() {
    $additional_text = ' More info';
    echo '<h2 class="woocommerce-loop-product__title">' . get_the_title() .$additional_text.'</h2>';
}
add_action('woocommerce_shop_loop_item_title','change_product_title');