The only official and standard way to access your Google Drive backup is by restoring it during a fresh WhatsApp installation. How to download WhatsApp backup file - Android Community
While Google Drive provides a secure cloud storage solution for your WhatsApp data, the platform does not allow you to "download" a backup file directly like a standard PDF or photo. Instead, the backup is stored in a hidden, encrypted partition of your account, designed solely for restoration via the WhatsApp application. download google drive backup whatsapp