Principally, if the alcohol is extracted from grapes or dates it is not permissible. Rasulullah (Sallallaahu Álayhi Wasallam) said, ‘Khamr (wine) is from these two trees, dates and grapes.’ (Mishkãt p. 317).
Furthermore, Rasulullah (Sallallaahu Álayhi Wasallam) said, ‘Alcohol itself is prohibited and intoxication in every other beverage.’ (Hidaaya vol. 4 p. 497).
In view of the abovementioned Hadith, since the alcohol in coke is from ethanol which is fermented from sugar cane mollasses and does not intoxicate, it is permissible. However, if one is doubtful, he may exercise precaution and abstain.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai