In Jain tradition, every true Jain monk or nun eats only strict Jain āhār (Jain food). That is part of their basic vows.

A few very well‑known examples (all followed only Jain āhār):

• Āchārya Vidyāsāgar Ji (Digambar) – extremely strict: one meal a day, no roots, no fruits, no milk, no oil, no sugar, etc. Only very simple Jain food taken in the palm of the hand. ( en.wikipedia.org)
• Muni Tarun Sagar Ji (Digambar) – famous for “Kadve Pravachan”; as a Digambar muni, he too strictly followed Jain āhār all his life. ( en.wikipedia.org)

Among laypeople (householders), many devout Jains keep very strict Jain food, but it is not usually publicly advertised who is “100% Jain āhār” all the time, so naming a specific businessman/celebrity as “only eats Jain āhār” can be inaccurate.

If your interest is mainly in what exactly counts as Jain āhār, you can see a simple explanation here and here .