We were seated a few rows from the back of the student section, and we had purchased one of those refillable cups that are larger than regular cups - around 32 oz. I had just brought it back from getting a refill with blue Powerade. I set it down, and 2 seconds later my wife kicks it over by accident. We both watch in terror as it makes its way down the stadium, and row by row everybody turns around looking back to see who the idiot was with the Powerade. Being a full cup, it traveled very far - was surprised how many rows it got to. Not knowing what to do with 20 rows of angry people turning and staring up at us - my wife and I both turned around too and looked up behind us, as if we were trying to figure out who it was.
It was pretty traumatizing, but we still laugh about it 6 years later.