Why do we always see water as mirage?

Yesterday I was watching a cartoon show. There one of the characters was walking on desert and suddenly he finds the mirage of water. He ran towards it as he was very thirsty but disheartened to find out that it is just the illusion. As I always think differently, I started to think why everyone travelling across desert always see WATER as the mirage? Why not milk or soft drinks?! ?????? ?????? It is all the work of our mind. Mirages are the form of an optical illusion which is caused by total refraction of light. As I mentioned it is an optical illusion, when we see a mirage, we first see a shining material in long distance. Now our mind starts to think what it could be? A mirror? A glass frame? Pond of water? As we are familiar with pond of water ( which is also the present need as we are in desert and we are thirsty ) ,our mind rules out the first two possibilities and arrive to the conclusion that it must be the pond of water ! That's why mirages are always WATER .