All polls see Prime Minister Netanyahu's Likud party and Gantz's National Unity party as the two biggest parties by far, with Yair Lapid's party trailing behind.
Cohen was in Sderot on Wednesday to rally support and show solidarity with local residents who have been targeted by dozens of Hamas rockets.
The bottle, thrown by the protesters towards the reporters Moriah Asraf Walberg and Yishai Porat, did not physically harm them.