Peeled and roughly cut into small the sweet potato.
Place the sweet potatoes in a large saucepan and add enough water to cover. Then boil over medium-high heat until tender about 15 minutes.
While boiling the sweet potato, chopped the apple into tiny pieces about 5 mm(0.2 inch).
Drain and place the potatoes in large bowl and add the sugar and the milk, then mash the sweet potatoes.
Add the chopped apple and mix until well combined.
Cut the spring roll wrappers in half. Take one sheet of the spring roll wrapper carefully and place horizontally.
Place about 2 tablespoon of the sweet potato filling on the spring roll wrapper in the front side. And paint some water along the edge in the back as glue, then roll up tightly.
Fold over both sides and press hard with wet hands. Repeat with the remaining rolls. As doing that, keep them all covered with plastic wrap to prevent from dry.
Preheat the vegetable oil about 2 cm on the large pan over medium heat. Fry the wrapped rolls in the oil until golden brown on both sides. Transfer rolls to a paper towel to soak up excess oil.