The importance of subsistence level trading has been drastically underestimated in all aspects of distance commerce of the premodern era. What many don't appreciate in the Roman period is that ships, even hardy seagoing vessels were cheap in comparison to premodern Early Modern times. The expense of a voyage therefore came not from the ship but from the cargo--from a practical standpoint, what this means is that it was not neccesary to carry only the most expensive goods for a journey to be profitable. Subsistence trading, in bulk, low value, but easily salable items like grain, was thus a viable strategy. very frequently, books on economic history that are not focused on ancient economies do not appreciate this, and the sort of teleological "ancient luxury trade progressing to modern bulk trade" is irritatingly common.

But to get down to actual evidence, I know of two easy examples of purely practical items being traded: rice and wood. Rice grown in India and Indian timber have both been found in Berenike, the best excavated port along the Red Sea. The rice is in high enough quantity that it was probably a fairly common trade good, an easy and cheap material a merchant captain could use to fill out his stores. The wood is somewhat more complicated. It is something of a truism that after a long distance a wooden ship will invariably need to be refitted and repaired, and this includes replacing timber. The timber removed from the ship can then be sold as lumber in port to help finance the repairs. However, given the disparity in wood resources between Egypt and India I find it extremely plausible that merchant captains sailing from India could stock up on lumber as a specific trade good.

When you go to the eastern half of the Indian Ocean information becomes much worse. SE Asian archaeology is in many ways less frustrating than South Asian, but it still lacks the funding and volume of material neccesary to answer many fine grained questions. Furthermore, the climate conditions of SE Asia make it notoriously difficult to conduct archaeobotanical research.

I am not actually aware of a single source dealing with low value goods in the Indian Ocean, so you would be best looking at Red Sea archaeology, particularly Sidebotham's Berenike. beyond that I can provide sources as you like.