How to add custom options of product in Magento 2

Here we learn, how to add custom options of product in Magento 2.

Note: We also have a separate module (Magento 2 Dependent Custom Options) that gives the ability to admin to create dependent custom options for the products. These options will be presented on the product page and will be dependent on one another. For more information, you can check it on our store.

I have created Drop-down Type custom option here.

$objectManager = \Magento\Framework\App\ObjectManager::getInstance();
$productId = 12490;
$product = $objectManager->create('\Magento\Catalog\Model\Product')->load($productId);
$productOptions = [
    [
        "is_delete" => '',
        "sort_order" => 1,
        "title" => "Size",
        "type" => "drop_down",
        "is_require" => 0,
        "values" => [
            [
                "sort_order" => 0,
                "is_delete" => '',
                "title" => 'M',
                "price" => 5,
                "price_type" => 'fixed',
                "sku" => ''
            ],
            [
                "sort_order" => 1,
                "is_delete" => '',
                "title" => 'L',
                "price" => 5,
                "price_type" => 'fixed',
                "sku" => ''
            ]
        ]
    ]
];
/**
 * Initialize product options
 */
if ($productOptions && !$product->getOptionsReadonly()) {
// mark custom options that should to fall back to default value
    $customOptions = [];
    foreach ($productOptions as $customOptionData) {
        if (empty($customOptionData['is_delete'])) {
            if (isset($customOptionData['values'])) {
                $customOptionData['values'] = array_filter($customOptionData['values'], function ($valueData) {
                    return empty($valueData['is_delete']);
                });
            }
            $customOptionFactory = \Magento\Framework\App\ObjectManager::getInstance()->get(
                'Magento\Catalog\Api\Data\ProductCustomOptionInterfaceFactory'
            );
            $customOption = $customOptionFactory->create(['data' => $customOptionData]);
            $customOption->setProductSku($product->getSku());
            $customOption->setOptionId(null);
            $customOptions[] = $customOption;
        }
    }
    $product->setOptions($customOptions);
}
$product->save();

That’s all.