REST API Response Modification to Include Custom Attribute

I’m currently using the following endpoint to retrieve the last 50 orders:

/rest/V1/orders/?searchCriteria[sortOrders][0][field]=created_at&searchCriteria[pageSize]=50

However, I’ve noticed that the product attribute “searchable_sku” is missing from the response for the products within the orders. How can I modify the API response to include this attribute?