Awoniyi put the visitors ahead in the 27th minute.
The 23-year-old has now scored one goal in seven league appearances for Union Berlin this season.
Ellyes Skhiri equalised for the hosts in the 36th minute.
Max Kruse netted the winning goal for Union Berlin 18 minutes from time.
Cologne paraded Tolu Arokodare for 10 minutes.
Arokodare took the place of Salic Oczan in the 83rd minute.
Copyright © 2020 NGNewsHub.com All rights reserved. The information contained in NGNewsHub.com may not be published, broadcast, rewritten, or redistributed without the prior written authority of NGNewsHub.com.