Gas cap was off through car wash?

About the only real way to be 100% sure would be to drain the tank. Would not be that bad as that car has fuel pump access inside so no dropping the tank, just remove the pump and look into the tank with a good light. Water would be pooled at the lowest point in the tank and could be removed by sticking a small tube into the pooled water and drawing it off.

But that car has an outer fuel door, did it get closed by the wash pressure? If it did I doubt much got in. If not I still doubt a lot got in as the flap at the top of the neck would block it and the actual nozzle opening isn't very large.
If you are in an area that uses alcohol in the fuel, that can help as it will absorb the water and let it pass through the system.

What I would do is get a couple bottles of old fashioned "dry gay" (basically alcohol) and pour in a bottle, run it to half tank or so, refill the gas and add the second bottle.

I kind of doubt much if any water got in tank, there is a flapper valve right at where pump goes in and nozzle has to open it to put gas in. It is to hold fuel vapor in, drive the car and do not worry about it.