$custom_options ="4:fixed:0:0;4.5:fixed:0:1;5:fixed:0:2;";



  $Products =  $productCollection->create()
             ->addAttributeToSelect(['id','sku'])
            ->addOrder('entity_id','desc')->load();


    foreach ($Products as $Product) {
          insertProductCustomOptions($Product->getId(), $custom_options, $custom_option_label, $Product->getSku(), 1);
       }


  function insertProductCustomOptions($product_id, $option_data, $option_title, $sku, $is_require) {
//

try{

    $objectManager = MagentoFrameworkAppObjectManager::getInstance();
// check if product option is already there
$product = $objectManager->create('MagentoCatalogModelProduct')->load($product_id);
$customOptions = $objectManager->get('MagentoCatalogModelProductOption')->getProductOptionCollection($product);
// Set option array
$allOptionsArray = $customOptions->getData();

$flag = 0;

// Collect all options values
foreach ($allOptionsArray as $allOpKey => $allOpVal) {



    if($allOpVal['title'] == $option_title) {

        $flag = 1;
        break;
    }
}
if ($flag == 1) {

    $optionValues = explode(';', $option_data);
    $options_arr = array();
    $cos = $co = array();
    foreach ($optionValues as $optionValue) {
        $optionValueData = explode(':', $optionValue);
        if (count($optionValueData) >= 3) {

            $optionValueDataLabel = $optionValueData[0];
            $optionValueDataPriceType = $optionValueData[1];
            $optionValueDataPrice = $optionValueData[2];
            $optionValueDataSortOrder = 1;
            if (count($optionValueData) >= 4) {


                $optionValueDataSortOrder = $optionValueData[3];
            }
            $option_sku = $sku . ' ' . $optionValueDataLabel;
            $options_arr[$option_sku] = array('title' => $optionValueDataLabel, 'price' => $optionValueDataPrice, 'price_type' => $optionValueDataPriceType, 'sku' => $sku . ' ' . $optionValueDataLabel, 'sort_order' => $optionValueDataSortOrder, 'exist_flag' => 0, );
        }
    }
    // Get all options
    foreach ($customOptions as $o) {

        if ($o -> getTitle() == $option_title) {
            $values = $o -> getValuesCollection();
            foreach ($values as $k => $v) {

                $option_sku_existing = $v -> getSku();
                if (array_key_exists($option_sku_existing, $options_arr)) {

                    $v -> setTitle($options_arr[$option_sku_existing]['title']) -> setSku($option_sku_existing) -> setPriceType($options_arr[$option_sku_existing]['price_type']) -> setSortOrder($options_arr[$option_sku_existing]['sort_order']) -> setPrice(floatval($options_arr[$option_sku_existing]['price']));
                    // set exist flasg to 1
                    $options_arr[$option_sku_existing]['exist_flag'] = 1;
                    $v -> setOption($o) -> save();
                    $cos[] = $v -> toArray($co);
                } else {
                    // remove all other skus which are not present
                    $v -> delete();
                }
            }
            // Option array
            foreach ($options_arr as $osku => $oval) {
                if ($oval['exist_flag'] == 0) {

                    // add those values which are not there already
                    $value = $objectManager->create("MagentoCatalogModelProductOptionValue");
                    $value -> setOption($o) -> setTitle($oval['title']) -> setSku($oval['sku']) -> setPriceType($oval['price_type']) -> setSortOrder($oval['sort_order']) -> setPrice(floatval($oval['price'])) -> setOptionId($o -> getId());

                    $value -> save();
                    $cos[] = $value -> toArray($co);

                }

            }
            $o -> setData("values", $cos) -> save();
        }
    }

} else {
    // add all new attributes
    $options_arr[$sku] = array('title' => $option_title, 'type' => 'drop_down', 'is_require' => $is_require, 'sort_order' => 0, 'values' => array());
    $optionValues = explode(';', $option_data);
    foreach ($optionValues as $optionValue) {
        $optionValueData = explode(':', $optionValue);
        if (count($optionValueData) >= 3) {
            $optionValueDataLabel = $optionValueData[0];
            $optionValueDataPriceType = $optionValueData[1];
            $optionValueDataPrice = $optionValueData[2];
            $optionValueDataSortOrder = 0;
            if (count($optionValueData) >= 4) {
                $optionValueDataSortOrder = $optionValueData[3];
            }
            $options_arr[$sku]['values'][] = array('title' => $optionValueDataLabel, 'price' => $optionValueDataPrice, 'price_type' => $optionValueDataPriceType, 'sku' => $sku . ' ' . $optionValueDataLabel, 'sort_order' => $optionValueDataSortOrder);
        }
    }
    $product -> setCanSaveCustomOptions(true);
            $product -> setHasOptions(1);
    foreach ($options_arr as $sku => $customOptions) {

        $option = $objectManager->create('MagentoCatalogModelProductOption')
                ->setProductId($product_id)
                ->setStoreId($product->getStoreId())
                ->addData($customOptions);
        $option->save();
        $product->addOption($option);
    }
     unset($options_arr);
     unset($optionValues);

  }

   }
 catch (Exception $e)
 {
  echo $e->getMessage();
 }