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If it was winterized correctly, there is no water in the hot water heater. DO NOT attempt to turn it on, at least electrically, in fact, do not attempt to heat the tank by any means unless you are sure it is full of water....
The tank is normally winterized by draining it completely and then setting the (winterizing) bypass valve(s) to bypass the tank. This saves you from filling the tank with 6-10 gallons of RV antifreeze which is not needed in an empty tank. There could be 1, 2, or 3 valves depending on the system used and they should be located nearby the tank itself. Without going into numerous instructions on the possible valve systems, check to see if you can locate them (or it) and let us know how many and we can go from there to set them correctly thus filling the tank itself. Knowing the Make and model of the water heater might be helpful too.