What proof would you need to support your cause on a soldier malingering ?

I would start likely with benefit of the doubt and being supportive. Instead of assuming the person is simply a malingerer just yet, what if they really do have issues but no doc is figuring it out? What if whatever the odd times this happens are actually triggers of a real condition? What if troop would do better if they could? Most people do well when they can. If they aren't doing well, what is the lagging skill or ability? Is it maybe not physiological issue, rather, this soldier and the army are not a good match for each other and both would be best served by breaking up, so to speak? So many variables. But if you really are a SGT, take this slow and think critically.

Best to refer to Command unless you are a provider.

If he’s getting quarters then wouldn’t that mean he actually has something wrong with him? The doctor isn’t just handing quarters out left and right. I have stomach issues myself. They arise at random times and there’s nothing I can do to stop them.

Refer to behavioral health for an evaluation. Impossible to say what’s going on. Maybe malingering. Maybe a genuine psychiatric disorder. Maybe ineffective coping. An eval should help shed. light on it.

If you believe the soldier is malingering (using sick call or the medical process to avoid duty), then escalate your concerns to to someone who can have a peer-to-peer discussion with the ability to investigate.

Think about it this way, unless you are a medical professional trained in that specific area can you make an educated opinion as to whether they are sick or just faking? Or is it just a hunch? If it is the former, document and present your EVIDENCE (you would already know what this is) up the CoC. If it is the latter, then present your CONCERNS to someone like your 1SG or PSG/Platoon Commander with the caveat of "something doesn't feel right about Benotz, can you ask Doc to pay special attention to his case?"

As you mentioned, it's at weird times. It could be environmental (exposure). It could be food allergies (something in the chow hall just 2 days a week). It could be anything. The doctors are going to have a better way of tracking and asking the correct questions.

Does this behavior coincide with less than desirable duties? That would show a pattern of behavior.
That said, it is always possible that troop has a real medical issue that they need addressed for their own health, but are just stubborn and won’t go to see Doc. If they are impacting your mission they can be helped over to medical, if for no other reason than looking out for their true welfare.

I do agree with some of the previous replies in that I wouldn’t go sneakiuaround trying to catch them in the act of malingering. If they are malingering it will show with no assistance.

You would think that he would need a command ordered physical evaluation. Without that you must take the Soldier's word that he is either sick or injured in some way.

The Soldier has to be medically proven to have nothing wrong with them by a couple of Providers. In today's environment with liberal interpretation of what constitutes allowable behavioral health issues, this can be a true leadership challenge.

Maybe you should just let it go. You don't want the reputation of following a soldier around trying to prove he's guilty of something. It might prejudice any real investigation showing that his leadership was out to get him.

Start Med Board paperwork on him.