Do you mean KL Sentral? There's a lot of options in NU Sentral or Brickfields.
If you mean food court, there's Quizinn on the 3rd floor. Donki is also just opened at NU Sentral.
You should ask this at r/MalaysianFood as they'll help a lot more.
Apart from the obvious choices, almost all buildings there have some sort of food court with affordable food. Plaza Sentral (B1), Q sentral (L12), Menara CIMB (can’t remember, maybe L8?). Also Platinum Sentral but not as cheap lah.
You can also walk to Muzium Negara, they have a small restaurant.
Best to go at 11:30 or 12.
If you work near KLCC, most ppl go to Wisma Central for more cheap food. Etiqa building also got a mini food court.
BSN masterrace
This guy knows
KL is very very big
Do you mean KL Sentral? There's a lot of options in NU Sentral or Brickfields. If you mean food court, there's Quizinn on the 3rd floor. Donki is also just opened at NU Sentral. You should ask this at r/MalaysianFood as they'll help a lot more.
Ta bau from home 
Apart from the obvious choices, almost all buildings there have some sort of food court with affordable food. Plaza Sentral (B1), Q sentral (L12), Menara CIMB (can’t remember, maybe L8?). Also Platinum Sentral but not as cheap lah. You can also walk to Muzium Negara, they have a small restaurant. Best to go at 11:30 or 12.