Install single package from Rawhide

yum install fedora-repos-rawhide
yum install --enablerepo rawhide bash

This is the top search result for this inquiry. Key signing has changed for F27 on, so to pull a package from rawhide use the following:

sudo dnf install fedora-repos-rawhide -y
sudo dnf --disablerepo=* --enablerepo=rawhide --releasever=[next release #, e.g. if you're on 27 use 28] install [package name]

You can also import the key manually from the Fedora website or force an unauthenticated upgrade to the newest fedora-repos.