get apt-cyg from :
rawgit.com/transcode-open/apt-cyg/master/apt-cyg
like this :
wget rawgit.com/transcode-open/apt-cyg/master/apt-cyg
then install to cygin bin
install apt-cyg /bin
now use apt-cyg form install packages , (install tmux in cygwin ) apt-cyg install tmux
GitHub : https://github.com/transcode-open/apt-cyg