Cover black-eyed peas with water, and soak overnight.
Heat vegetable oil in a large saucepan over medium heat. Stir in garlic and onion, and cook until softened, about 4 minutes. Stir in flour until evenly combined with onion. Add water, nutmeg, and sugar. Drain peas, and add to saucepan. Bring to a boil over high heat, then reduce heat to medium-low, and simmer until the black-eyed peas are tender, about 30 minutes.