Preheat the oven to 150*C. Lightly coat 2 wire racks with non stick cooking spray. Core the apples. Peel them if you wish. Slice the apples into rings, about 5mm thick. To keep the apple rings from browning, add them to the water and lemon juice, making sure each apple ring gets coated with the water-lemon mixture. Let stand for 5 minutes. Drain well; pat the apples dry with paper towel. Arrange the apples in a single layer on the wire racks, making sure the rings do not touch or overlap. Set each rack on a backing sheet and bake for 15 minutes. Reverse positions of the baking sheets from the top oven rack to the bottom rack and vice versa. Bake for 15 minutes more. Turn off the oven. Let the apple rings dry in the oven, with the door closed, for 3 hours. Remove from oven. To store, place apple rings in large plastic bag and seal.