Are they the plastic bottle or the polypro type? If I have a bad water bottle, I usually put some bleach in it and fill it up with water and let is sit awhile. Then rinse throughly. If it persists, I replace the bottle. It sounds to me like bacteria is causing the odor and soap will not necessarily kill it. Try a little bleach and water. Afterall, chlorine is what they use to clean the water anyway. Hope that helps ya!