Can Ghouls drink water? I just started watching the series and I'm about 4episodes in. 

In episode 2 the shopkeeper old guy says: 


   Since ancient times, coffee is the one thing that ghouls and humans can enjoy. 


but in episode 4 when Touka got a piece of meat from a friend, she was in the bathroom drinking water and fighting to keep it in her body. 

She didn't instantly vomit from the water but in episode 1 when the protagonist drank milk he did. 

So based off of these observations, can ghouls actually drink water &amp; coffee? And if so are there other dietary things that float along this median line of edibility among both races?
Although what you said is write but think about this "Coffee is not just made up of only coffee beans, it contains water as well".