Shred sweet potato and onion.
Rinse potato/onion mixture under cold water, then strain. Place a cheesecloth or clean dishtowel over potato mix, and squeeze to release as much liquid as possible. Discard liquid.
In large bowl, combine sweet potatoes, onions, eggs, sugar, matzo meal, cinnamon, gently mix well by hand.
Heat oil in a large heavy skillet to 375 degrees. Scoop about 1/3 cup of mixture and drop in hot oil. Cook about 2-3 minutes on each side until golden brown. Drain on paper towel or resting rack.