This looks like an Aircraft Fuel Servicing Cart, which transfers fuel from an underground network to the aircraft. There are two types of vehicles that transfer fuel at larger airports with these fuel networks:
(image source: Wikimedia)
Aircraft fuel servicing hydrant vehicles do not have tanks. These vehicles
connect to a pressurized ...
My guess would be that this is a bowser used for aircraft de-fueling.
Sometimes, very seldom though, aircraft need to be de-fueled to lower the weight for take-off. For example: if the aircraft is refueled for a flight to a destination and back (which is common for various reasons), but for some reason the payload for the first leg increases, the aircraft ...
That looks like the ground heating/cooling rig. It is a long flexible hose that connects to the plane (snf the other end connects to a heater or cooler. This way the plane does not have to run the engine or the APU at the gate.