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.
If it is proven that coca cola is mixed with something which may intoxicate if it is drunk on its own, then coca cola is forbidden otherwise no. However, if you avoid drinking it in order to stay away from doubtful things, then this is something religiously praiseworthy. The Prophet said: "Whoever avoids the doubtful matters, safeguards his religion and honour.'' [Al-Bukhari and Muslim].
As regards the narration which you asked about in the question, it is authentic and it is reported by At-Tirmithi, An-Nasaa'ee, Abu Daawood, Ahmad and Ibn Maajah .
Its meaning is also confirmed in another narration which reads: "Any kind of intoxicant (which causes drunkenness) is forbidden." [Al-Bukhari and Muslim]. The expression ''any kind of intoxicant'', includes a small quantity and a big quantity.
Allaah Knows best.