That’s not going to work to your favor, and even if it does it will never be reliable as physics tends to intersect and penetrate and having many small balls in a confined moving space is like worst case scenario for the engine.
I think your best bet is morph targets and cleverly made fluid blend shapes (as Darthviper suggested), then blend between those to simulate the effect of fluid in a ball. It wont be perfect but if it’s a stylized look then it may work better.
I don’t think you can get a better option than this with what the engine can offer you out of the box.