How dangerous is taking a bath in Coca Cola?
Cola and soft drink products are generally in the pH=2.5-3.5 range.
This is the same pH range as vinegar, lemon juice and most fruit juices. Note apple itself is around 3.0-3.5, so it is not about some magical trick of food industry to kill us all. 

Does Cola dissolve your body traceless? No.
Do you want to soak your body in it for hours? Would you soak your body in vinegar for hours? Or even water...