Heat oil in a large nonstick skillet over medium-high heat. Add garlic; cook until golden (about 30 seconds), stirring constantly. Stir in water, cumin, coriander, and turmeric. Cover, reduce heat, and simmer 7 minutes. Add shrimp; cook 3 minutes.
Combine flour, sugar, salt, and yogurt; stir with a whisk. Stir yogurt mixture into shrimp mixture. Cover and cook 4 minutes or until shrimp are done. Stir in onions.