If you drink expired milk, you will most likely not experience any ill effects. Milk is a highly processed food and contains many preservatives that prevent it from going bad. However, if the milk has been stored in an environment that is too warm or humid, it may spoil and cause nausea, vomiting or diarrhea. If you are unsure whether the milk is still good, it is best to err on the side of caution and throw it out.