cleanEmailFields.CreateDummyEmails.cls

 public static void cleanEmailFields(Map < String, List < String >> mSobjField) {
  // Iterate through SObject->Email Fields 
  for (String sObjName: mSobjField.keySet()) {
   // Build a list of all fields that need to be queried
   List < String > lstEmailFields = mSobjField.get(sObjName);
   // Generate a SOQL query to get records with non null emails
   String soql = createSOQL(sObjName, lstEmailFields);
   List < SObject > sObjRecords = new List < SObject > ();
   // Iterate through SObject records
   for (SObject sObjRecord: Database.query(soql)) {
    // Iterate through email fields found on SObject and replace with dummy values
    for (String strField: lstEmailFields) {
     String strEmail = (String) sObjRecord.get(strField);
     if (String.isEmpty(strEmail)) continue;
     sObjRecord.put(strField, strEmail.replaceAll('\\W', '_') + '@invalid.invalid.co');
    }
    sObjRecords.add(sObjRecord);
   }
   update sObjRecords;
  }
 }