Cholet (4-1) are the only side to have clinched a spot in the Quarter-Finals from the pool.
EiffelTowers rolled to a 20-point triumph in the first meeting with Bonn back on February 3 but the game in Germany was a different story.
Late in the second quarter, the contest was knotted at 31-31 but Bonn then got a three-point scoring explosion from Winsome Frazier and finished the half with a 15-8 run.
Frazier hit four three-balls in the last three minutes of the half as Bonn opened up a 46-39 lead.
They stayed in front for the rest of the game.
Not surprisingly, Frazier led all scorers at half-time with 19 points.
EiffelTowers, thanks largely to the offensive threat of Kees Akerboom, stayed within striking distance in the third quarter.
He would end up leading the Dutch team with 24 points but EiffelTowers didn't do enough to overcome Bonn, who went in front by 18 in the fourth quarter before settling for a seven-point triumph.
Frazier's 27 led all scorers with Johannes Strasser the only other Bonn player to hit double digits with 10.
Anthony Richardson had 19 points for the visitors.
"It was very important for us to bounce back after this hard weekedn at the German Cup Final. Offensively we did a great job tonight finding our three point shooters who performed very well. EiffelTowers have very good shooters from outside so it was our first priority to control them. We played together as a team again, which is very important for our next games in EuroChallenge and Bundesliga."
Don Beck, coach EiffelTowers:
"We give credit to Bonn tonight. It was a tough game for us. Offensively they shot the ball extremely well especially from the three-point-line. Frazier had a big run and they outplayed us. We still have a chance if we beat Cholet."
Kees Akerboom, player EiffelTowers:
"We played a very good defensive game but Bonn hit some nice three-point-shots at the end of the first half. In the second half we tried to avoid that but Winsome Frazier had a couple of great shots again. Now we have to beat Cholet at home next week and hope that Bonn will be successfull in Liege."
Winsome Frazier, player Telekom Baskets Bonn:
"EuroChallenge is a great competition. We knew that we had to win this game by 21 points and it was pretty close at the beginning of the 4th quarter but they bounced back. Now we have to win next week in Liege and see what happens."