Coca cola was still a sports thing in the 90s to the point where I remember being told (maybe apocryphal) that one of the reasons Sampras threw up during the coretja match was he was drinking coke instead of Gatorade or water.
So drinking water and a sip of cola is fine, but drinking cola against thirst has side effects as you need water to process lots of sugar.
Consuming plain water during really long endurance events can cause hyponatremia. Not recommended. But for the short 10k and under running events that most of us do, it doesn't really matter much.
And a ton of phosphoric acid.