I don’t know if this helps the sensory issues or the digestive ones and I don’t care. I was prescribed a medicinal crazy straw for the sensory integration issues. The biggest mechanism of action is something something ear fluid pressure, but there are other, subtler ones.* At this point I don’t know why it works and I don’t care: sucking on the crazy straw makes me feel better and less sensitive to noise. Even if it’s a placebo effect, I can’t think of what damage I could possibly do to myself drinking through a crazy straw, so I’m not questioning it.
My bonus discovery was that straws seem to help with digestion/nutrient absorption too. Most vitamin dosages are too high for me, so I spill some of the contents into water and drink that. If I take too much, I get symptoms ranging from “stomach ache” to “vaguely icky.” If I drink that water with a straw, I can take a higher dose (of anything) than if I drink the water directly.
My hypothesis is that sucking stimulates the “nutrients are incoming” reflex that chewing is supposed to, and thus my gastrointestinal system is more prepared to accept and use the bounty I am giving it. This definitely falls under “plausible but not proven”, but it seems to be working for me.
*The sensory therapist was not good at Science, and I was in shock after doing the evaluation, so my recollection of her statements is not of much value here.