In July 2023, what world record did race car driver Jake Hughes break?

The indoor speed record! He drove 218.71kph (135.9mph) inside London's ExCeL Centre.
(I never knew there was such a record.)
https://www.espn.com/f1/story/_/id/38086304/formula-e-driver-jake-hughes-sets-indoor-world-speed-record

NEOM McLaren Formula E Team driver Jake Hughes, hit 218.71km/h to become a Guinness World Record holder for the fastest speed achieved by a vehicle indoors.

The speed was over 50km/h faster than the previous record. The record was made on a 346-metre straight section of an indoor racetrack in a Formula E GENBETA car, a modified version of Formula E's current GEN3 car which are both electric vehicles.

https://www.mclaren.com/racing/formula-e/jake-hughes-sets-a-guinness-world-record-for-the-fastest-speed-indoors/