Find unread emails in gmail and copy sender and subject in a google doc

downloadUnreadEmails.gs

function downloadUnreadEmails() {
  var sheet = SpreadsheetApp.create('Unread Emails');
  sheet.appendRow(['Sender', 'Subject']);
  
  var threads = GmailApp.search('is:unread');
  
  for (var i = 0; i < threads.length; i++) {
    var messages = threads[i].getMessages();
    
    for (var j = 0; j < messages.length; j++) {
      var message = messages[j];
      var sender = message.getFrom();
      var subject = message.getSubject();
      
      sheet.appendRow([sender, subject]);
    }
    
    threads[i].markRead();
  }
  
  var url = sheet.getUrl();
  var exportUrl = url.replace(/edit$/, '') + 'export?format=xlsx';
  var token = ScriptApp.getOAuthToken();
  var response = UrlFetchApp.fetch(exportUrl, {
    headers: {
      'Authorization': 'Bearer ' +  token
    }
  });
  
  var blob = response.getBlob();
  var file = DriveApp.createFile(blob);
  file.setName('Unread Emails.xlsx');
}