I have done this before so don’t feel bad. I put almost half a gallon of rainx in the coolant. The system is big enough to were that small amount in the overflow will not harm your engine. If you can drain the reservoir and replace with concentrated coolant not 50/50 and you will be fineI opened the hood, saw the yellow cap on the left, opened it and started to pour windshield washer fluid in it. and that is when i realized the other BRIGHT YELLOW cap that has a windshield washer symbol on it. I quickly pulled back the jug, and said the F word out loud.
I probably poured about 1-2 cups in there. Should I go get it flushed right away? From what I read on Google, most says it'll be fine, but some can turn the coolant into gel.