Hydrox is a cream-filled chocolate sandwich cookie currently owned and manufactured by Leaf Brands. It debuted in the United States in 1908, and was manufactured by Sunshine Biscuits for over 90 years. Hydrox was largely discontinued in 1999, three years after Sunshine was acquired by Keebler, which was later acquired by Kellogg's. In September 2015, the product was reintroduced by Leaf Brands.
Oreo was created in 1912 as an imitation of Hydrox. Oreo eventually exceeded Hydrox in popularity, which resulted in the Hydrox cookies being perceived as an Oreo off-brand. Compared to Oreos, Hydrox cookies have a less sweet filling and a crunchier cookie shell that is reportedly less soggy in milk.