A "Case Study" content type includes an entity reference field "field_related_product," to associate each Case...

Add "field_related_product" to the Product content type and use css to display the field in the sidebar region

Add *ne "show related content" block to the Product nodes display Set it to include only nodes of type "Case Study."

Create a view of Product nodes, with a relationship to field_related_product, and add the title field using the relationship Add the block to the Product nodes display

Create a View of Case Study nodes, with a relationship to content referenced from field_related_product, and a contextual filter by ID using the relationship, set to use "Content ID from URL." Add the block to the Product nodes display