Does someone have an explanation for this?

It looks like the liquid inside the cup is absorbing the heat from the flame, preventing the cup itself from burning

The liquid absorbs the heat and keeps the cup from burning. It works fine with water and other containers. I’ve done it with water in a styrofoam cup with no problems. I’ve seen people boil water in grocery bags too.

Strawberry juice is the main ingredient of the Spacex rocket heat shields.

Imagine if it was pineapple juice. We could launch it to the sun and it wouldn't burn.

Plastic cups vs hot ball

The juice makes it self healing? Or it’s magic

Ok but can we talk about strawberry juice? Lol That is not a thing. Atleast not in USA.

It works woth water too. No strawberries needed. I've cooked eggs in paper cups inside of fires multiple times. The wax (now plastic) that keeps the paper from getting soggy can't burn off because the water keeps it from doing so. Heat is transferred to water.

Water transfers heat better than air. It's why we use water as a heat transfer (hydronic heating) and air as an insulator.

Strawberry juice has flame retardant properties, that's why fire fighting aircraft drop it on forest fires. 😏