I hope this may helps you
After add to cart run this code:
use Magento\Framework\Session\SessionManagerInterface;
use Magento\Framework\Stdlib\Cookie\CookieMetadataFactory;
use Magento\Framework\Stdlib\Cookie\PublicCookieMetadata;
use Magento\Framework\Stdlib\CookieManagerInterface;
in constructor:
CookieManagerInterface $cookieManager,
CookieMetadataFactory $cookieMetadataFactory,
SessionManagerInterface $sessionManager,
After product was added to cart
$metadata = $this->_cookieMetadataFactory
->createPublicCookieMetadata()
->setPath('/');
$sectiondata = json_decode($this->_cookieManager->getCookie('section_data_ids'));
$sectiondata->cart += 1000;
$this->_cookieManager->setPublicCookie(
'section_data_ids',
json_encode($sectiondata),
$metadata
);
Before trying above code try with frontend/section.xml :
<action name="NAMESPACE/MODULE/CARTUPDATE/">
<section name="cart"/>
</action>