You accidentally put window washer fluid in the coolant container - what's the damage?

Probably no damage, especially if you only filled the reservoir with it and not the whole cooling system. Use a turkey baster and suck up what's in the reservoir, dispose of properly. Then refill with coolant. I'm really not sure if the washer fluid will screw with the various rust inhibitors or lubricants key to the coolant. If you're really concerned, just flush the coolant and refill the system.