When taken care of by washing and drying properly after each use, odors are less likely to develop. If you store food in them for a while, they may retain some odor, but this is only for a short period. To remove the odor, wash the bottle. Then, put some white vinegar in it. Cover it, and shake it. Next, let it sit overnight. Rinse it out with warm water in the morning, and let it dry.