Bravo was unbeaten on 73 while Brathwaite made 55 as the duo added 82 runs for the second wicket on the second day in reply to a Pakistan Cricket Board (PCB) Patron's XI first innings total of 308 all out.
The day-night practice game is being played with a pink ball to give the West Indies preparation for the first Test, a day-night affair starting in Dubai from October 13.
Earlier, the Patron's XI added 67 runs to their overnight score of 241-5 with Adnan Akmal scoring 69.
Leg-spinner Devendra Bishoo finished with 5-107 and paceman Jason Holder took 3-38.
West Indies lost Leon Johnson for 11 before Bravo and Brathwaite defied the attack. Bravo hit 12 attractive boundaries and two sixes while Brathwaite's knock had four boundaries.
At the close Shai Hope was unbeaten on 24 and West Indies trailed by 134 runs.
For the Patron's XI paceman Ahmed Jamal and leg-spinner Shahzaib Ahmed took a wicket apiece.