What kind of medicine can I take for sore throat while breastfeeding?
Depends on the cause
If you have a pretty bad sore throat associated with fever, red throat, rash, or other symptoms, see your doctor. If it is just a scratchy sore throat in the morning that goes away pretty quickly in the day, then any thing that is moisturizing is fine-liquids, honey, sore throat lozenges, etc.
If it is due to allergies, treat it like you would any allergy. Most otc anti-histamines are safe.