Download the package: http://www2.futureware.at/~nickoe/msys2-mirror/msys/x86_64/rsync-3.1.2-2-x86_64.pkg.tar.xz
Launch Git Bash and change to the download location.
Extract the archive using coommand:
tar -xf rsync-3.1.2-2-x86_64.pkg.tar.xz
You will get a folder usr.
Move usr/bin/rsync.exe to C:\Program Files\Git\usr\bin
Source:
How to Add rsync to Git Bash for Windows 10. https://gist.github.com/hisplan/ee54e48f17b92c6609ac16f83073dde6