First time: drink 1/2/2= 1/4 water and 1/4 fruit juice in the cup. After adding water, water: pure juice = 3: 1.
The second time: drink 3/4/3 =14 of water and juice 1/4/3*2= 1/6. After adding water, 5/6 of the water in the cup is completely consumed.
So the total amount of drinking water:1/4+1/4+5/6 = 32/24.
The ratio of water to fruit juice: (32/ 24):( 1/2)=8:3.