I know that doctors over here say that acne has nothing to do with eating junk food, but some doctors think that an overload on diary products can cause cystic acne. I know if I have too much dairy (milk, pizza, etc) a couple days in a row.....then i start to break out.
I went to the derm doctor a few months ago and she examined my skin and could tell I wasn't drinking much water because the skin wasn't as resilient in some areas. And she said that when you don't drink enough water.......you skin becomes dehydrated. So, your brain tells your skin to start producing excess oil in order to "hydrate" your skin. And then that oil clogs your pores........leading to pimples.
So loading up on sufficient water can't hurt:)