In a 2-quart heavy saucepan combine sugar, water, and corn syrup. Cook and stir over medium-high heat until mixture boils. Clip a candy thermometer to the side of the pan. Reduce heat to medium; continue cooking, without stirring, until the thermometer registers 260 degree F, hard-ball stage (10 to 15 minutes). (Adjust heat as necessary to maintain a steady boil.)
Remove saucepan from heat; remove thermometer. In a large mixing bowl beat egg whites with a freestanding electric mixer on medium speed until stiff peaks form (tips stand straight). Gradually pour hot mixture in a thin stream over egg whites, beating on high speed about 3 minutes; scrape sides of bowl occasionally. Add vanilla and, if desired, food coloring. Continue beating on high just until candy starts to lose its gloss (5 to 6 minutes). When beaters are lifted, mixture should fall in a ribbon that mounds on itself.
Drop a spoonful of candy mixture onto parchment or waxed paper. If it stays mounded, the mixture has been beaten sufficiently. If mixture flattens, beat 1/2 to 1 minute more; check again. If mixture is too stiff to spoon, beat in a few drops hot water until candy is a softer consistency. Immediately stir in candied fruit. Quickly drop remaining mixture onto waxed paper. Store tightly covered for up to 1 week. Makes about 40 pieces.