We have shown that water addition to a cobalt-based hybrid coordination network crystal leads to a significant decrease in its melting point and glass transition temperature significantly. Through calorimetric, spectroscopic, diffraction, XAFS, and simulation methods, we have proposed a mechanism for the water-promoted breakdown of the internal network of Co 2+ ions and bisacetamide organic linkers, while the [CoBr4] 2-centers remain relatively intact. The former is obtained by replacing labile Co-O bonds from the organic ligand with coordination to water molecules. We also probed the effect of water addition on the melting behavior of two related hybrid coordination network systems with exchanged transition metals and charge balancing anions, showing a similar decrease in melting temperature and thus confirming the universality of the mechanism. This mechanism resembles that of water and other network "modifiers" in traditional oxide glass-forming systems, where such structural modification is used to design and tune glass properties for industrial applications. As such, the present results pave the way for a significant expansion of the meltable and glass-forming hybrid systems as well as substantial nonstoichiometric chemical diversification of these systems.