Can leaving room temp water in bottle for a day go bad?

If you have sterilized the bottles and the water by boiling them, then you should have no troubles after one day. I think if you wanted to be safe you could boil all your water once a day and leave one bottle out to get to room temperature. Fill up all other bottles and put them in the fridge. When you use up the one bottle, take out another one from the fridge and by the time your baby is ready to eat, the water will be room temperature.