Returning a response

Both Sitemap and SitemapIndex implement Laravel's Responsable interface, so you can return them directly from a route or controller:

use Spatie\Sitemap\Sitemap;
use Spatie\Sitemap\SitemapIndex;

Route::get('sitemap.xml', function () {
    return Sitemap::create()
        ->add('/page1')
        ->add('/page2');
});

Route::get('sitemap_index.xml', function () {
    return SitemapIndex::create()
        ->add('/pages_sitemap.xml')
        ->add('/posts_sitemap.xml');
});

This will return an XML response with the correct text/xml content type.