I have IBS. The annoying part is it does vary person to person. Each day a food I thought is safe could be randomly unsafe and cause what the doctors call a flare up. Those are the worst case scenario.

Dairy, gluten, high fibre, spice, are common triggers. Vegan foods are generally safer (vegan burgers with no spice or mayo) are easier options.

Fruits and vegetables are commonly harder to digest so avoid those. Plain simple food.

Google FODMAP diet for an indication of what is commonly eliminated.

Vegan food (no dairy or gluten) is usually ok to eat. White long grain rice is safe, fish is great, turkey, chicken and lean meats are good.

Ask what the person usually eats. If they aren't managing their IBS they're going to be in a world of pain. Without medication and eating safe my health physically and mentally is awful.

TLDR, Vegan food. No dairy. No spice. No gluten. No green vegetables. No sulphorics. No nightshades. No tomato. No pepper. Google FODMAP Google IBS. Ask that human what their triggers are as it varies.

THIS IS ONLY MY EXPERIENCE. I AM NOT A TRAINED MEDICAL PROFESSIONAL OR THAT SPECIFIC HUMAN. PLEASE DO NOT MESSAGE ME WITH NONSENSE.