Bring a large pot of water to a boil. Add diced Buddha's hand, return to a simmer, and cook until citrus softens, about 30 minutes. Drain.
Combine Buddha's hand, 2 1/2 cups sugar, and water in the same pot; bring to a simmer and cook, stirring occasionally, until syrup reaches a temperature of 230 degrees F (110 degrees C). Remove from heat and cool to room temperature. Drain citrus; pour excess liquid into jars and reserve.
Spread drained citrus out onto a wire rack and let dry until tacky, at least 24 hours. Pour remaining sugar into a shallow bowl. Toss citrus in sugar until coated; transfer coated pieces to a plate to dry, at least 2 hours.