Sensitivity to sweets in a tooth is a classic sign of a leaky filling. Fillings, especially amalgam fillings, as they wear and corrode, can begin to allow nutrient substances and bacteria to get between the filling and the tooth. These gaps become sensitive to sweet substances that penetrate down to the sensitive part of the tooth beneath the surface.
If this is the cause of your symptom, replacing the filling will ordinarily solve the problem.
Places on your teeth where the enamel has worn or has been recently polished can also cause sensitivity to sweets. If this is the case, the sensitivity should get better with time. If this is the case, a toothpaste for sensitive teeth can help alleviate the problem.
Other sensitivities and related subjects: