We tend to underappreciate how important hydration is for the recovery process of a common cold or a sore throat. However, it is fundamental to keep ourselves hydrated at all times. During a common cold, the water losses are superior to those experienced in normal circumstances, and that contributes to a sore throat for the reasons we have described above.
Thus, if we keep hydrated, this effect will be reduced, and the same will happens with our symptoms. You can stay hydrated by drinking more herbal infusions, drinking electrolyte beverages especially designed for mild dehydration, and eating more high-moisture foods.