There are devices called aspirators which use a stream of water to create a vacuum by the venturi effect. They basically consist of a T connector with the suction inlet at right angles to the the water flow. Across the joint the water flow is constricted, which accelerates it, dropping the pressure and creating suction.
The vacuum pressure generated is fairly modest and they use quite a lot of water but they are extremely simple. But if you need the vacuum to do a significant amount of work this may not be adequate. However is you can include a source of compressed air in your system then much higher pressures are possible using the same principal.
What is practical really depends on the context, for example whether you want discrete pulses eg to pick something up with a suction cup or a continuous suction more like a vacuum cleaner. In many cases a self contained electric vacuum pump will be the most convenient solution.
Obviously there is ultimately the possibility to operate a vacuum pump or piston via a hydraulic motor or actuator.