Heat the oil in a large skillet over medium heat. Fry the mustard seeds in the oil until they begin to splutter, 2 to 3 minutes; add the curry leaves and asafoetida powder and cook together for 1 minute before adding the onion, potato, green chile peppers, turmeric, sugar, and salt. Cook and stir the mixture until the potatoes are tender, about 10 minutes.

Crumble the rice into the skillet, breaking the grains apart as best you can. Stir the rice into the mixture, continuing to separate the grains your spoon as you stir; cook until the rice is thoroughly heated, 2 to 3 minutes. Add the lime juice and cilantro to serve.