I guess it could be safe to drink an occasional Coke depending on what you mean by occasional. But keep this in mind. Coca-Cola is not a benign substance.
It’s not as if you simply don’t get nutrition by drinking one. In fact, your body must strip calcium from its bones to metabolize the Coke and get it out of the body. The sugars — and worse, high fructose corn syrup– lower the immune system dramatically contributing to diabetes, adrenal exhaustion, infertility, autism, allergies and plaque in your arteries. If this isn’t enough to convince you, consider that Coca-Cola is an excellent agent for stripping rust off of cast iron and paint off of your car!