If I had a 2nd bottle, I would mix this 'epoxy' (AKA liquid glass) I can get locally and add a tint, partially fill and do it as a slush cast. All 2 part resins are exothermic, and given the heat they give off, you would not want to fill the bottle like these with that because of the risk of plastic warp. Bit this stuff stays cold, even after degassing. And it sets hard. For a display piece, this would be "Perfect".
I would be concerned that it would warp the bottle once it cures.