。
She explained the product with everything she had.
Literal
She [topic-は] with-all-one's-might this product [of-の] explanation [object-を] did.
説明をする vs 説明する: both work, but the をする form (treating 説明 as an object noun) slightly emphasizes 'an explanation' as a discrete event, while plain 説明する flows as a single verb. この商品 frames the scene — a sales pitch, demo, or training context where speaker and listener share the referent. 商品 ('merchandise, product') is the standard retail term, distinct from 製品 ('manufactured product') and 品物 ('goods').