Heat a large saucepan of water to boiling. Add the snap peas and cook 2 to 3 minutes. Drain and rinse under running cold water. In a large skillet over medium-low heat, cook the garlic in the oil until golden. Remove and discard the garlic. Add the sugar snap peas and fresh or thawed peas and cook until tender, 3 to 5 minutes. Remove from heat and add the mint, sugar, and salt.