Fuel is typically stored in the wings, so as it depletes, it doesn't change the center of gravity of the plane with regard to the lift. Center of gravity is very important in smaller planes.
But there's really not that much sloshing or shifting of liquids after takeoff. The tanks can be segmented, but just like being able to walk in a plane, there's not a lot of shifting overall. It's a constant pull backwards, but that's about it.
Smaller planes with bathrooms use a more camp toilet kind of system, with less liquid, which is all generally stored and held in the same part of the plane, so no shifting of weight in a large scale. I've been in a 6-seater with a lavatory, and we were basically told to hold it because the crew didn't want to clean the tank. But it was all in a stack in the same part of the body.
This is how the South African apartheid government of a minority of whites controlled everyone else. They pitted the Asians again the mixed race people, and both of them against the blacks. All about trying to maintain the spot of least harassed, most relatively privileged group.