My Dear Pogo,
You can drink whatever you want! Unless some doctor said, "Don't drink anything else except water," then continue to drink whatever it is you like, along with water. I drink coffee, milk, orange juice, Canada Dry diet ginger ale, water, and sometimes iced-tea or lemonade. For lactose-intolerant people who can't drink milk, there is a milk product called "Nu-Trish" for them.