Apparently, one of the music composers of the film, Ankur Tewari didn't wanted Kunal, as he thought that Ganjawala would not fit the criteria of the track. Though the producer and actor of the film, Aftab Shivdasani was confident about him. Thus being a close friend of the singer he recommended Ganjawala to Ankur and was successful in convincing him.
Ankur gave a brief to Kunal of the kind of voice he was looking for- a husky tone, and Kunal like a professional singer did not even think for once and started having cold stuffs like ice cream and cold water. The day he got cold, Kunal went for the recording of the song.
Now, the gifted singer is not telling us the track and is playing a guess game, as he has sung 4 tracks in the album it's hard to guess which one is sung with a bad throat, as all are wonderfully sung.