I think the acid in the soda might keep things safer than expected..bacteria don't like acid. ^^ Yogurt is fermented with bacteria that produce acids and sits out at room temperature overnight..same thing with cheese.. But things can always go wrong, so it might be good to skip that step =)warm soda and milk sitting overnight for 15 hours is probably something that would make me sick
It'll be neat to watch the reaction sped up! =D