function addVideoToYouTubePlaylist() {
  // Read the source videos from Google Sheet
  var sheet = SpreadsheetApp.getActiveSheet();
  var data = sheet.getDataRange().getValues();

  // Add your own playlist Id here
  var playlistId = 'PLAYLIST_ID_HERE';

  // iterate through all rows in the sheet
  for (var d = 1, l = data.length; d < l; d++) {
    // Add the video the existing playlist
    YouTube.PlaylistItems.insert(
      {
        snippet: {
          playlistId: playlistId,
          resourceId: {
            kind: 'youtube#video',
            videoId: data[d][0],
          },
        },
      },
      'snippet'
    );

    // wait for a second to avoid hitting the rate limit
    Utilities.sleep(1000);
  }
}