Hi,
While there is no option for that, you could add a line like this:
if(!empty($product->skip_google_products)) continue;
after the line:
foreach($products as $product) {
in the file plugins/hikashop/google_products/google_products.php
Then, create a custom field of the table "product" and of the type "checkbox" with one value and with the column name "skip_google_products" so that when the checkbox of that custom filed is checked in the product, the product will be skipped by the Google products plugin.
Note however that this modification will be lost when you update HikaShop. So you'll have to reapply it after updates.
We'll look at doing something for this in a future release.