Brian Ashcraft of Kotaku tells us that on the Buddhist holiday of Obon in August, many Japanese people create figures out of eggplants and cucumbers in order to welcome visitation by the spirits of the dead. Cucumbers represent horses and eggplants represent cows. The spirits arrive quickly on cucumbers, but leave slowly on eggplants.
So it logically follows that twitter user @sativa_high would recreate the vehicles used by the War Boys in Mad Max: Fury Road with these two vegetables.