Craft\EntryModel and its behaviors do not have a method or closure named "siteUrl"
Environment variables are only available in specific settings, and Entry URL Formats are not one of them.

There’s no need to include your Site URL in there anyway, though. The field’s label might be a little misleading – it’s really more of a URI format than a URL format.

If you want your entries to get URLs like http://example.com/entry-slug, then all you need to put in your section’s Entry URL Format setting is:

{slug}