Favorite beverage would have to be a beer(too many to choose from), but when detecting a lot of times I go just after sunrise so I guess I have coffee more often.
I bought one of those beer holder sleeves that golfers use to put in their golf club bags, and I have affixed it to my At-pro. It hold 6 beers, and keeps them nice and cold. I make sure to pull off all the tabs and throw them on the ground, and then throw the empty cans in front of the park lawnmower as it goes by. After that I use my detector as a crutch to stumble my way home. Seriously I just bring some good ol' drinking water.
I never carry drinks with me while detecting or hiking. There are enough springs seeping through the mountains to drink from. So many people have never drank spring water. No chemicals added. A friend told me of guests from the city and mentioned they were going up the road to the spring to get some water. The city folk had no idea what they were talking about.