The bizarre attacks included one person being hit in the face with an apple while walking along Bohemia Road in Hastings, on 12 April.
Another was struck in the arm with a tomato while walking along Firle Road in Eastbourne the following evening.
Later the same day a further two attacks happened in The Bourne, Hastings, one involving a person being hit in the head with a tomato and another with an unknown object – both causing serious injuries.
A Sussex Police spokeswoman said: “Most of these attacks have occurred during daytime hours when the victims have been out alone in open and in public places.
“In all cases the victims have been going about their daily routine when they have been hit by items believed to have been thrown or propelled in some way from a vehicle.
“There have been no links established between each of the victims, however it is believed that these incidents are part of a series.
“We are asking any witnesses to come forward, as well as any further victims.”