No, because the liquid in the water bag is not ordinary water and contains conductive substances. The thermal energy generated by electromagnetism is sealed to prevent leakage. If electricity is applied, a magnetic field will be generated. mutual reactions create eddy currents and hysteresis in the so-called water, then thermal energy is generated.
The reason a transformer generates heat is due to hysteresis and eddy currents. People make transformers out of pieces of rigid silicon sheets to reduce hysteresis and eddy currents, thereby improving the efficiency of the hot water bottle. so it will generate heat after being turned on.
If replaced with water, it will not generate heat because water is a poor conductor, so the liquid in the bag cannot be replaced with water . The refillable hot water bag cannot bere used only after filling it. with water. After filling, air must be released. It expands quickly when charging, and if the quality is not good, it is prone to short circuit or even explosion.