Most days of the week, water. When it's an adult beverage, it's homemade apple wine to go with the homegrown tobacco I normally smoke. I have heard that you can make a quick and dirty moonshine in small batches on your stovetop from the lees, bad batches, etc.
I usually have a tea or ice water with a pipe if it is just me. If I am over at my neighbours then it is a nice peaty scotch. You can't really miss- if it is enhancing your enjoyment of the smoke, then do it.
Coffee or tea in the morning and daytime. Beer or bourbon in the evening. I don't drink water while smoking. I drink close to a gallon of water a day as it is, I don't want to drink it when enjoying a pipe.