I made this material for my potions. It works perfectly with spherical containers, other shapes may have some problems. The idea is simple: find a center of your container, then apply level and slosh offsets to it. Everything above the resulted height will be transparent.
After you recreate this material, adjust CenterOffset to match it with the center of your bottle. PotionLevel controls amount of liquid. 0 value will make it half full.
Physics will be a bit harder to do, but it’s quite achievable with some simple scripting.
](&d=1553419063&type=full)