Take the wheel out, hold the sides that are closest to straight, then whang the bentest bits hard on the ground, might take a couple of goes, but it should straighten out a fair bit, then get cracking with a spoke key.
And yes, I have actually done this on someone else’s bike, while out for a ride along the K&A Canal. Poor girl was having to walk along holding the back wheel of the ground, so I took the wheel out and belted it on the ground a couple of times.
Got the wheel straight enough to ride with the brake disconnected.
She was chuffed to bits, she was still several miles from home.