Butter a straight-sided 8-inch square cake pan and set aside. Line with a single sheet of parchment paper.
Attach a candy thermometer to the side of a saucepan. Add the sugar, corn syrup and 1/4 cup water to the pan and bring to boil, stirring until the sugar has just dissolved. Continue to cook until the syrup reaches 255 to 260 degrees F on the candy thermometer.
Meanwhile, in the bowl of an electric mixer fitted with a whisk attachment, beat the egg whites until stiff peaks form.
When the syrup reaches temperature, slowly (and carefully) drizzle it into the egg whites with the mixer on high. Once the syrup is fully added, pour in the vanilla and continue to beat until the mixture is no longer glossy and holds its shape, 7 to 8 minutes.
Remove the bowl from the stand mixer and, moving quickly, fold 1 cup of the gummy candies into the mixing bowl using a wooden spoon. Transfer the mix to the prepared pan and do your best to spread into an even layer--it will be very sticky. Sprinkle the remaining candies over the top, lightly pressing them in to ensure they stay.
Allow the divinity to cool completely, about 1 hour. Cut into 1 1/2-inch squares and store in an airtight container.