Why do my teeth feel sensitive to cold drinks?

Either. You have a cavity, eating too much food that are highly acidic eg tomatoes, lemons, excess soda drinks can result in acid eating away at tooth enamel, you may have receding gums exposing nerve endings and aggressive brushing can cause breaks in the enamel causing tooth sensitivity.Brush lightly & use softer toothbrushes may address your problem.See dentist if concerns not resolved.
Variety of reasons. There are different reasons as to why someone 's teeth are sensitive to cold. Receeding gums and dentin exposure is one reason. You will need a thorough examination by your dentist to rule out any other causes.