It has been a yearly tradition for Kamen Rider to appear in Oronamin C's Commercial. Even this year Kamen Rider Saber's Cast & Riders appear to promote the Drink.
Since Kento is fallen into the dark side as Kamen Rider Calibur in TV Series, I was expecting it would be Touma, Rintaro & Yuri who will be appearing in the commercial currently. But turns out I was wrong. Espada Kento appears in the Commericial along with his Raimei-Ken Ikazuchi.
There is along a Web Movie where the three swordsman are seen reading a Secret Book titled "Oronamin C Story" which contains the details of the secret & taste of Oronamin C.