Refrigerator: store leftover hot chocolate in an airtight container in the fridge for up to 5 days. Freezer: you can freeze hot chocolate for up to 2 months. To thaw, transfer to the fridge overnight. To reheat: you can reheat in a slow cooker on low heat until warm. Or, add to a pot and warm over low heat, stirring very frequently. Single portions can also be warmed up in the microwave.