Preheat oven to 180 degrees C. Grease a 23x33cm baking dish.
Scatter the apples, peaches, plums, and strawberries into the bottom of the prepared baking dish, mixing the fruit well. Sprinkle with 1 tablespoon of sugar and 1/2 teaspoon of cinnamon if desired. Pour the water over the fruit.
Mix together the butter, 1 cup of sugar, the apricot nectar, flour, rolled oats, plain biscuit crumbs, and 1 tablespoon of cinnamon in a bowl until the mixture is crumbly and well combined. Sprinkle the crumbly mixture over the fruit.
Bake in the preheated oven until the topping is lightly browned and the fruit is tender, about 45 minutes.