Dennis started the game and was replaced by Siebe Schrijvers two minutes before the hour mark.
It was Dennis’ seventh appearance of the competition for the Belgian outfit.
Okereke came in for Luis Openda in the 73rd minute.
He came close to getting a goal four minutes later but shot wide from inside the box.
Adem Buyuk put Galatasaray ahead in the 11th minute, while Kreppin Diata equalised for Brugge deep into stoppage time.
Brugge maintained third position in the table with three points from five games and boosted their chances of securing an Europa League berth.
At the RZD Arena, Bryan Idowu was benched for 90 minutes in Locomotiv Moscow’s 2-0 home loss to Bayern Leverkusen of Germany.
Locomotiv who suffered their fourth defeat of the competition occupy bottom spot in Group D with three points from five games.