Both teams shot below 30 percent in the first half, combining to make just eight points in the final 7 minutes before the break. Green Bay opened the second half on a 13-2 run, leading by 12 points with 15:52 left to play.
The Cougars climbed back in front and led by one point with 2:49 to go. Alfonzo McKinnie and Sykes each made a jumper to put the Phoenix ahead by three, and Chicago State missed three 3-point attempts to end it.
McKinnie had 13 points and Carrington Love added 10 for Green Bay (11-3).