All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
It is not permissible to consume something which contains alcohol or other intoxicants whether the consumer becomes intoxicated or not and whether this led to a disease or not, as this is using intoxicants which one must get rid of. Allaah Says (what means): {O you who have believed, indeed, intoxicants, gambling, [sacrificing on] stone altars [to other than Allaah], and divining arrows are but defilement from the work of Satan, so avoid it that you may be successful.}[Quran 5:90]. Therefore, one must avoid any intoxicant whether it is a small or big quantity.
As regards the existence of alcohol in coca cola drink, then we are not aware of this, and we have not come across any statement of trustworthy experts on this issue. So, in principle it is permissible to consume coca cola unless there is a reason of prohibition like being an intoxicant or causing harm.
With regard to transforming alcohol to another substance, then the jurists agreed that if wine is transformed to another substance without any treatment, then it takes the ruling of the substance to which it was transformed, because the reason of its prohibition is intoxication, and this reason disappeared, and the ruling depends on the reason which makes it prohibited, and when there is no reason for its prohibition then it is not forbidden.
Nonetheless, the jurists differed in opinion about wine being transformed to another substance with a treatment, the most preponderant opinion is that it is not permissible to treat it; this is the view of the Shaafi'ee and Hanbali schools, and the narration of Ibn Al-Qaasim from Maalik because when the Prophet was asked about taking wine as vinegar, he replied: "No." [Muslim] Furthermore, the Prophet ordered us to spill intoxicants, and Allaah ordered us to absolutely avoid them, and if we treat them we are not avoiding them.
Allaah Knows best.