My dad used to do things like this all the time, I can remember one in particular from when I was maybe 6 or 7 years old. He and my stepmom were having a beer with another couple at the house. Getting up to grab another, my dad headed to the kitchen, motioning for me to follow. Rinsing his empty can out, he filled it with water and asked me if I wanted to play a joke on our guests....of course I did.
We headed back out into the living room where our guests were waiting. My dad, holding the water filled beer can, took a swig and then, to the horror of the couple, offered it to me. I turned it up and gulped it down as fast as I could, while my dad howled with laughter.
After they were able to pick their jaws up off the floor, my dad mercifully let them in on the joke, and I think they laughed....I know I did. I was so proud to be a part of my dad's prank.