I suppose that you could drive around and just see things from the outside, but DC rush hour is a nightmare and can run as late as 8:30 - 9:00 PM and you've then got the reverse in the AM.

You will have missed the Smithsonians, but there are plenty of evening things in DC. Why not pick one thing you want, such as the Washington Monument, stay somewhere walking distance such as the JW Marriott on Pennsylvania Avenue, Uber from DCA to the hotel, walk to the monument and back and relax. Uber to DCA in the AM. Tons of great restaurants and you could have an Uber simply take you up to the Capitol to let you wander around (outdoors) if you wanted to do that as well.

Car rental will be expensive and parking either impossible or eye-poppingly expensive.