Anthony

This plugin will limit access to the site. Only visitors with a cookie token will be able to access the public website. Visitors without the cookie will see a “coming soon” style of page.
You can customise the “coming soon” content, and you can change the way tokens work. Visit yoursite.com/?add_token to receive the token allowing you to see the site. To remove the limited access, simply disable this plugin.
By default, the token is “letmein”. So use these links: 
site.com?letmein 
site.com?takemeoff
This plugin is useful when you’re developing your site. You can work on your live web server without having your site open to the public.

Token Access

Limit access to the site to those with a cookie token.  Visitors without the cookie see a customisable "coming soon" style of page.

Hinaloe

<blockquote>
You no longer have to use this plugin because it was merged to <a href="https://ja.wordpress.org/plugins/public-post-preview/" rel="nofollow ugc">PPP plugin</a> at v2.6.0.
</blockquote>
This plugin send <code>Cache-Control: no-cache, must-revalidate</code> header when show <a href="https://wordpress.org/plugins/public-post-preview/" rel="ugc">public-post-preview</a> post.
In other word, that make skip cache of CDN (like CloudFlare, CloudFront… and other), or Proxy-Cache (Like Nginx). 
So, outside people always can see newest draft, and there is no need extra time to close public draft.
This plugin needs PHP 5.3+
Note: If you’re using CloudFront, you should also use <a href="https://wordpress.org/plugins/c3-cloudfront-clear-cache/" rel="ugc">C3 Cloudfront Cache Controller</a>

Non Cache Public Post Preview

Disable cache when show public post preview post

Token Access vs Non Cache Public Post Preview