Windshield Washer Reservoir Capacity -> 176 fl oz (1Gal + 48 oz)
2017 Gen 2 Volt (Red)
To estimate the Windshield Washer Reservoir Capacity I first siphoned out as much fluid as I could (little over 1/2 gallon of the blue stuff, fortunately not the orange or yellow used for brutal upstate deep of winter).
Next, I ran the windshield washer and wipers to empty (nice clean windows). It took five or so cycles (~10 second cycle max where it turns off by itself) to go to minimum flow, and I quit there. There are about three full 10 second cycles remaining (~30 seconds total of spray) after the low windshield washer fluid low warning message in the driver information console (DIC).
Then, I poured in 1 Gallon of tap water (128 oz). After that, it took another 3 full 2 cup (16 oz measuring cup) portions (16 oz each) to reach the very top part where the first taper is (just below the cap).
So, (bells and whistles here), I estimate the capacity to be about 128 + 48 oz, or about 176 fluid ounces!
Some water may have flowed into the system (below the bottle), however I did not prime or run the system with water in it. So the estimate might (?) include a little system capacity beyond the bottle.