TOPIC:

I  want to start my son on MMS. He takes immunotherapy infusions once a month. I know he should not take MMS on infusion day, but what about every other day? And also, what is a good juice to use 4 oz instead of distilled water?

No one really knows the answer to your question with any real certainty or surety.

I would assume every other day would be okay, ALTHOUGH I would probably
skip the day after, too, at least, to give the immunotherapy (whatever it is)
some time to work.

Maybe you could inquire how long after the treatment the treatment works,
or is in the body, etc., however that works, so you know how long to wait.

You can use other liquids, but they are all different, and they can even
be changed by the companies, usually without warning.

So it would be best to get some ClO2 Test Strips (see my website, link below, under Products),
so you can check to make sure the liquid you choose isn't negatively affecting the potency of the MMS.

The liquid should not contain Vitamin C / citrus or caffeine or alcohol or chocolate or milk
or too much antioxidants.
That is a general suggestion, but an important one.
(there is a list to avoid in Jim Humble's "MMS Health Recovery Guidebook", and some suggestions)

I still haven't tested Plant-Based Milks, which I would think would be good
to disguise and cover the taste and smell, and probably be very drinkable.

Maybe a non-nut version (like not almond, e.g.), since they tend to be higher in antioxidants. (?)
(maybe Oat Milk? -- Uh, oh: Oats are high in antioxidants called avenanthramides,
not found in other cereal grains. These antioxidants reduce inflammation and relax arteries,
improving heart health. The soluble fiber in certain oats can keep blood sugar from rising after a meal.)

Or chicken or beef or vegetable broths.