Boil sugar, lemon juice and water in a medium saucepan. Add diced fruit; cook, stirring occasionally, over medium heat until tender, 10 to 15 minutes. Stir raspberries into mixture and remove from heat. Let cool completely and then store in a pint jar in refrigerator for up to 1 month. Spread jam on croissants and crackers, stir into yogurt or spoon onto ice cream sundaes.