Revo
Finance

function doGet(e) {
  const cb = e.parameter.callback;
  const id = e.parameter.id;
  if (!id) {
    const out = cb ? cb + '("revo-ok")' : 'revo-ok';
    return ContentService.createTextOutput(out)
      .setMimeType(cb ? ContentService.MimeType.JAVASCRIPT : ContentService.MimeType.TEXT);
  }
  const gid = e.parameter.gid || '0';
  const ss  = SpreadsheetApp.openById(id);
  let sh = ss.getSheets().find(s => String(s.getSheetId()) === String(gid)) || ss.getSheets()[0];
  const data = sh.getDataRange().getDisplayValues();
  if (cb) {
    return ContentService.createTextOutput(cb + '(' + JSON.stringify(data) + ')')
      .setMimeType(ContentService.MimeType.JAVASCRIPT);
  }
  const csv = data.map(r => r.map(c => '"' + String(c).replace(/"/g,'""') + '"').join(',')).join('\n');
  return ContentService.createTextOutput(csv).setMimeType(ContentService.MimeType.CSV);
}