You can get products either from a subscription, or using the appropriate order, since the subscription object is an extension of the class WC_Order.
$subscription_products = $subscription->get_items();
$order_products = $subscription->order->get_items();
In most situations when you provide subscription services, both of them will be equivalent or $order_productsshould contain at least all the products found in $subscription_products.
; , $subscription->order WC_Order.