Guess I'd go with baking soda, over vinegar in copper pipes. When we had trailers with copper pipes we used baking soda. We never had that kind of reaction with copper and antifreeze. Different experiences, I guess. Sounds like a good cleaning for your water heater might solve the problem there?
We had a bad experience with blowing our lines the one year we tried it: replaced the water pump in the spring..... Many people do it though with good success.
Haven't ever tried vodka in the copper pipes.... sounds pricey!