This was originally developed by Zephirworks and forked here to keep up-to-date.
cd ~/Library/Application\ Support/Sublime\ Text\ 2/Packages/User
wget --no-check-certificate https://raw.githubusercontent.com/mattiasgeniar/Varnish.tmbundle/master/Syntaxes/VCL.tmLanguage
cd ~/Library/Application\ Support/Sublime\ Text\ 3/Packages/User
wget --no-check-certificate https://raw.githubusercontent.com/mattiasgeniar/Varnish.tmbundle/master/Syntaxes/VCL.tmLanguage
Restart your Sublime text. That's it!