I have successfully rooted cuttings in water with a couple drops of hydrogen peroxide added. Change the water often and add a couple drops of peroxide each time.
Hydrogen peroxide is a water molecule with an extra oxygen molecule. When it is added to water, the extra oxygen molecule is released so, for a breath period of time, the water is oxygenated. That helps cuttings grow roots.
But, Hydrogen Perixide will also destroy tissue (that's why it sizzles when you put it on a wound) so 2 - 3 drops is all you should add.