You can create a new blob in memory with the Utilities Service:

function createNewBlob() {



  var blobNew = Utilities.newBlob(initial data);

  blobNew.setName(BlobTest);



  Logger.log(blobNew.getName());



  blobNew.setDataFromString(Some new Content);



  Logger.log(blobNew.getDataAsString())



  var newFileReference = DriveApp.createFile(blobNew);

  newFileReference.setName('New Blob Test');

};

You can also create a new file, with some small amount of data, then change the content. In this example, a file is created in the root directory with the contents abc. Then the content of the blob is set to something else.

function createNewBlob() {



  // Create an BLOB file with the content abc

  var blobNew = DriveApp.createFile('BlobTest', 'abc', MimeType.Blob);

  Logger.log(blobNew.getName());



  blobNew.setContent(Some new Content);

  Logger.log(blobNew.getBlob().getDataAsString())

};

You could create data in memory, then create the blob with the finished data.