What Would Happen, If the sun were Made of Bananas!
The sun is hot, it is because its enormous weight creates vast gravity putting its core under colossal pressure, just as a bicycle pump gets warm when you pump it, the pump increases the temperature. Enormous pressure leads to enormous temperature.
If instead of hydrogen, you get a billion billion billion tons of bananas and hung it in space, it would create just as much pressure and therefore just as high a temperature. So it would make very little difference to the heat whether you made the sun out of hydrogen or bananas.
The heat caused by internal pressure would be similar to that of our sun. However, if its not made of hydrogen, the fusion reaction that keep it going wouldn’t get under way, so a banana sun would rapidly cool down from its initial heat rather than burning for millions of years.
As mentioned above instead of hydrogen we can use banana or furniture of enormous weight to create vast gravity putting its core under colossal pressure.