Fiyero would absolutely do something like that. He's not entirely new to the concept of electricity, but it wasn't common enough in Oz for him to know all the common sense stuff. He does know it can be dangerous - which us also why he's wary of the microwave.

"Oh, thanks," he answers, still a little distracted as he accepts the bottle of water from Kitty. He opens it and takes a sip, then immediately does a spittake as he realises it's not in fact water. And some of this not-water definitely went in Kitty's direction, causing Fiyero to look rather alarmed and sheepish.