Combine the sweet potatoes with the water in a pot and soak for 30 minutes.
Remove the potatoes from the water. Bring the water to a boil and return the potatoes to the boiling water with the ginger slices. Cook the potatoes at a boil until fork-tender, 20 to 25 minutes. Stir the sugar into the water until completely dissolved. Remove the sweet potatoes to individual bowls and spoon the ginger syrup over the potatoes to serve.