It comes days after the party leader was covered in a caramel shake while campaigning in Newcastle.
Bus driver Michael Botton told Kent Live: "There were a couple of guys standing with milkshakes, they were going to throw them over him.
“But the police are there, we’ve spotted them and now Nigel isn’t getting off the bus.”
Three young men were said to have been seen carrying the drinks at the Rochester campaign stop, reportedly with covered faces.
After Farage and his security detail were alerted, the Brexit Party leader was advised not to get off the bus.
According to Kent Live, the ex-Ukip man did eventually get off the bus, but stayed close to the vehicle as he spoke to supporters.