Exclude sigle post from sitemap.xml

On my clients page, I add an option to add entries with canonical tag to an external pages (because of the SEO). Is there a way to exclude single blog entry from autogenerated sitemap? I know, I can exclude the single page, but is there an option to do so with blog entry? Or the only option is to manually generate sitemap?

No, but that’s actually not relevant. The sitemap is just a convenience for bots, it doesn’t define what bots will index.

You can you this technique instead-