My Kingsnake seems to enjoy being misted sometimes too. I use a pump mister rather than a spray bottle (best $5 I ever spent by the way) and when I'm misting his enclosure he often comes out to see what I'm up to and will often just slither through the stream of water. I don't intentionally spray or mist any of my snakes, including my King, but if he crawls into the stream I don't stop him. My BP HATES when I mist near him, so I take him out when I mist his enclosure.
Anyway... to answer your original question about the bubbles: I would chalk this up to being sprayed, however, I would monitor the snake very closely and make sure that's all it was. Also, look for signs like elevated head, more bubbles, mucous build up, mucous smeared on the glass and/or water bowl and hides/decorations. My guess is all is fine, but I would just watch carefully and wouldn't hesitate to make a vet appointment if any other symptoms appear.