There are many ways how can H-bonds be broken. For example, they can be broken by heat. Just imagine water in liquid state and gass state. They can be broken by another molecule that is reacting with the molecule that is conected with H-bond.
Note: what is H-bond anyway?
A hydrogen bond is the electromagnetic attractive interaction between polar molecules, in which hydrogen (H) is bound to a highly electronegative atom, such as nitrogen (N), oxygen (O) or fluorine (F).