I made this quick little thing:
No complex ball needed, just a weighted bottom. I had to mess around with some strengths and velocities to make it work.
I can continue developing this if you'd like.
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I guess we're all working on it then !
The problem with your version is that it doesn't take in consideration fluid dynamics, and the issue of center of mass. By putting such a heavy weight on the bottom you nullify entirely the challenge of the bottle flip
I did this on my side
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Here's the mod if anyone wanna play around with it (It's not very polished yet, i just wanted to try to tinker with the concept)
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Please refrain from posting only two words, let's keep it constructive guys !