Used by Debian-like Linux distros, will get configured under guest's /var/cache/apt/archives.

To manually enable it:

Vagrant.configure("2") do |config|
  config.vm.box = 'some-debian-box'
  config.cache.enable :apt

Please note that to avoid re-downloading packages, you should avoid apt-get clean as much as possible in order to make a better use of the cache, even if you are packaging a box since the downloaded packages are actually stored on the host machine.