I'm not all that surprised. Coke is about as harsh a cleaner as you can get.
Short story. I have a co-worker of mine in Utah that was doing some testing with an automotive customer. We handle electronic components. They were working on a thermostat application and the sensor was going to be immersed in coolant. Part of the testing before they approved the thermistor was to not only make sure there were no ill effects from the hot coolant but also from any other fluids or additives someone put into their reservoir.
I'm not sure of the exact fluids tested, some acids, OTC coolant products and whatnot. In the end, the only thing that ate through the sensor and ultimately failed the test was Coca-cola.
While it may clean an engine, with today's assortment of electronics, you may want to think twice before pouring a 12 oz. can into your seized engine.
P.S. I drink water, tea and juice.