It is possible to send bulk tweets from Google Spreadsheet using Google Scripts. To get started, you need to include the OAuth1 libarary in your project, create a new Twitter app on apps.twitter.com and pass the Consumer Keys and API Secret to the Google Script project.

function sendTweet(user, tweet, tweet_type) {
  var twitterService = getTwitterService_();

  // If the Google Apps user has authorized the Twitter service
  if (twitterService.hasAccess()) {
    // Remove @ from the Twitter user name, if found
    var twitterUser = user.trim().replace(/^\@/, '');

    var api = 'https://api.twitter.com/1.1/';

    // Send a public @tweet or direct message (DM)
    if (tweet_type === 'DM') {
      api += 'direct_messages/new.json?screen_name=' + twitterUser + '&text=' + encodeString_(tweet);
    } else if (tweet_type === 'TWEET') {
      tweet = '@' + twitterUser + ' ' + tweet;
      api = 'statuses/update.json?status=' + encodeString_(tweet);
    }

    var response = twitterService.fetch(api, {
      method: 'POST',
      muteHttpExceptions: true,
    });
    if (response.getResponseCode() === 200) {
      Logger.log('Tweet sent');
    } else {
      Logger.log('ERROR: ' + JSON.parse(response.getContentText()).errors[0].message);
    }
  }
}

// Google Script has trouble sending tweets that contain !*()'
// so we replace these variable from the status text
function encodeString_(q) {
  var str = q;
  str = str.replace(/!/g, 'Ị');
  str = str.replace(/\*/g, '×');
  str = str.replace(/\(/g, '[');
  str = str.replace(/\)/g, ']');
  str = str.replace(/'/g, '’');
  return encodeURIComponent(str);
}