Have you looked at the pH of the water? I discovered filtering my tap water was making it acidic with a pH of 5! You could try alkaline water or coconut milk, just to see if it is the liquid and reflux or whether it is a separate effect of the chemistry of the water?
It does seem to just be the water. Milk didn't effect me, but it apparantly has a similar pH to tap water at it's lowest range. Alkaline Water is a bit hit and miss as to whether it makes me better or worse, and as I mentionned, Gaviscon Advance worsens it too. I don't apply a filter to my tap water unless I specifically pour it into my alkaline jug filter, so it's just bog-standard, nationwide water.
I'm not so sure pH is the problem, since I'm worse with water than, say a potato waffle or fish. It's probably not liquid reflux-based either, since it's an immediate reaction only seconds after I swallow.