How to grab meshes with Nvidia FLEX water inside?

Hi! I’m trying to make a project with realistic water which you can pour from one cup to another.
I’ve made a simple grab system like in this tutorial: Unreal Engine 4 Tutorial - Pickup and Drop Objects (Physics Handle) - YouTube
but a problem I’ve bumped into is when you pickup the cup or when you move with it all the water is getting out of the cup. Any ideas how I can solve this?


The cup currently has an auto generated convex collision. Water is a flex particle emitter.