In sunny locations I've heated water to well over 140F using these 3 items:

*Large Reynolds oven roasting bag
*black plastic bottle--half quart size works best
*Titanium (or Aluminum) stove wind screen (reflector)

Make a half-circle reflector with stove wind screen & place in oven bag. Add water bottle to bag--between reflector & sun location. Close/seal the bag & place in sunny spot 1-3 hours.

Caution: depending on location and "cook" time, water can get quite hot!