Here is how to build a model of sloshing in a tank using Explicit Dynamics. It may not be better than Fluent, but it seemed like a simple model to build.

Start with a surface model of the tank. I drew a 1x3x1 m rectangular five sided box. Create a solid body to represent the water in the tank. I drew a 1x3x0.5 m rectangular solid. In DesignModeler, change the water body from Solid to Fluid. I then used symmetry to model one half. Let's try to model the case where the sloshing is caused by the rectangular tank having a sinusoidal motion along the length of the tank. In Workbench, drop an Explicit Dynamics block on the Project Schematic. Apply the material properties to the tank and the water. Add a gravity load. Add supports. In this example, hold three edges, and paste tabular input from a spreadsheet of the time, x, y and z displacements. I created a sine wave function that has an amplitude of 20 mm and a period of 2 seconds. I edited the default contact from bonded to frictionless on the sides of the tank. Configure Analysis Settings to set the end time and the report time. Solve. After 1 hour of compute time to get to 2 seconds, I plotted the body of water at the 1.74 second mark. Watching the animation is better.

HereÂ is how to build a tank model in Fluent. Looks like a lot more steps to me.