mod_vhost_alias

<VirtualHost *:80>
  # get the server name from the Host: header
  UseCanonicalName Off
  ## insert a dummy name
  ServerName catchall.host
  # ServerName wiki.example.com
  ServerAlias *.*.*
  # ServerAlias *.*

  # this log format can be split per-virtual-host based on the first field
  # using the split-logfile utility.
  LogFormat "%V %h %l %u %t \"%r\" %s %b" vcommon
  CustomLog "${APACHE_LOG_DIR}/access.log" vcommon

  # 0     the whole requested host name 'foo.acme.com' if that was the requested domain
  # -2  the penultimate part 'acme' of foo.acme.com
  VirtualDocumentRoot "/var/www/clients/%-2/%0/w"
  VirtualScriptAlias  "/var/www/clients/%-2/%0/cgi-bin"
  # DocumentRoot "/var/www/clients/example.com/wiki.example.com/w"

  <Directory "/var/www/clients/*/*/w">
    Require all granted
    Options Indexes FollowSymlinks
    AllowOverride All
  </Directory>
</VirtualHost>