Intention is in the heart. It does not have to be said verbally. Eating Suhoor is an indication of the intent. However, if one does want to make a verbal intention, there is no reason to stop them. One could say:

وبصوم غد نويت من شهر رمضان ۔
“I intend to fast tomorrow for Ramadhān.”

If one stays hungry and thirsty, without intending to fast, the fast will not be counted.

Extracted from A Gift for Ramadhan, Page 49.

A Gift For Ramadhan – New 3rd Revised Edition