You can use Google Apps Script to post status updates (tweets) to Twitter.

This example generates an OAuth 1.0a HMAC-SHA1 signature that is converted to base64 and is passed to the Twitter API via an HTTP POST request. You can use it to send tweets from Google Addons, Google Sheets and standalone web apps.

/*
 * Post to Twitter from Google Apps Script
 * Code by @rcknr
 */

function postTweet(message) {
  var method = 'POST';
  var baseUrl = 'https://api.twitter.com/1.1/statuses/update.json';
  var props = PropertiesService.getScriptProperties();

  var oauthParameters = {
    oauth_consumer_key: props.getProperty('CONSUMER_KEY'),
    oauth_token: props.getProperty('ACCESS_TOKEN'),
    oauth_timestamp: Math.floor(new Date().getTime() / 1000).toString(),
    oauth_signature_method: 'HMAC-SHA1',
    oauth_version: '1.0',
  };

  oauthParameters.oauth_nonce = oauthParameters.oauth_timestamp + Math.floor(Math.random() * 100000000);

  var payload = {
    status: message,
  };

  var queryKeys = Object.keys(oauthParameters).concat(Object.keys(payload)).sort();

  var baseString = queryKeys.reduce(function (acc, key, idx) {
    if (idx) acc += encodeURIComponent('&');
    if (oauthParameters.hasOwnProperty(key)) acc += encode(key + '=' + oauthParameters[key]);
    else if (payload.hasOwnProperty(key)) acc += encode(key + '=' + encode(payload[key]));
    return acc;
  }, method.toUpperCase() + '&' + encode(baseUrl) + '&');

  oauthParameters.oauth_signature = Utilities.base64Encode(
    Utilities.computeHmacSignature(
      Utilities.MacAlgorithm.HMAC_SHA_1,
      baseString,
      props.getProperty('CONSUMER_SECRET') + '&' + props.getProperty('ACCESS_SECRET')
    )
  );

  var options = {
    method: method,
    headers: {
      authorization:
        'OAuth ' +
        Object.keys(oauthParameters)
          .sort()
          .reduce(function (acc, key) {
            acc.push(key + '="' + encode(oauthParameters[key]) + '"');
            return acc;
          }, [])
          .join(', '),
    },
    payload: Object.keys(payload)
      .reduce(function (acc, key) {
        acc.push(key + '=' + encode(payload[key]));
        return acc;
      }, [])
      .join('&'),
    muteHttpExceptions: true,
  };

  var response = UrlFetchApp.fetch(baseUrl, options);
  var responseHeader = response.getHeaders();
  var responseText = response.getContentText();
  Logger.log(responseText);
}

function encode(string) {
  return encodeURIComponent(string)
    .replace('!', '%21')
    .replace('*', '%2A')
    .replace('(', '%28')
    .replace(')', '%29')
    .replace("'", '%27');
}