I have recently observed in my trip between Dadar-YPR in Chalukya express. The train did not have pantry and one could see way side station vendors getting all possible brands including Bisleri, Aquafina, local brands etc.
In any case people were more than happy to pay for the same. At least they were charing the MRP which was Rs 20/- as compred to Rail neer which sells for Rs 15. Saw some of the stalls in stations selling other brands as well