I don't know the scientific answer to this, but I do know that in the past when I've had a sore throat both hot and cold liquids have been very soothing to me.
For cold liquids, cold fruit juices in particular can feel really good. During the worst throat pain I ever experienced I remember eating cold slices of watermelon constantly as it was the only thing that seemed to help.
And in regard to hot liquids, hot herbal or lemon tea with honey is extremely soothing. Unlike cold liquids, I often find that with hot liquids the soothing feeling lingers for a while, too, so that is an added bonus.
Hot or cold, you should definitely avoid dairy products or anything else that is in any way creamy, or at least my experience has always been that they seem to worsen the discomfort.