For Juicers: Can soy milk be substituted with water?

We went on vacation and there was a juice bar. My husband fell in love with the juice bar and he finally convinced me to buy a juicer. Well, I am looking for recipes and it seems that almost all the ones he would like have soy milk or almond milk in the recipe.
Is it necessary? Can they just be substituted with water?
I would appreciate any recipes anyone has that is a hit with your family.
Fruit or vegetable, or a combo would be appreciated.
Especially anything that you know can actually camouflage the taste of Kale.