Mostly in my right hand but if I'm holding something heavy like a grocery bag, I'll hold my drink at the left and I use my right hand to carry as my right hand is for whatever reason, slightly bigger and can lift more than my left.
If it's tea, I need to hold my cup in both hands. If it's water, right hand, beer or alcoholic beverage, left hand. Gosh, I've never thought about it until now.