The products need an existent brand in the Seller Center platform so firstly it's necessary to get the valid brand list.
$brands = $sdk->brands()->getBrands();
foreach($brands as $brand) {
$brandName = $brand->getName();
$brandId = $brand->getBrandId();
$brandGlobalIdentifier = $brand->getGlobalIdentifier();
echo sprintf('Brand: %s (ID: %s | Global Identifier: %s)\r\n', $brandName, $brandId, $brandGlobalIdentifier);
}