HI Lazaruszi 
Since it’s my clip, I better explain how I did it 
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It’s a trick. / illusion.
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Carrara particles have NO Volume,. they’re flat, and don’t build up. ...so,. you need to fake it.
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The Glass has an object inside it (the fluid) and that object has a couple of Morphs, to make it “Fill Up” the glass.
the main particle emitter, uses a “Meta Particle” which looks like a fluid / liquid. and the particles collide with the glass.
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The “fluid” object in the glass, is animated to change the morph and “Fill the glass”.
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Hope it helps 