Modeling Magic is what we use for seashells. It should easily work for fruits which already have lower center of gravity usually. Its a very maleable but dries into something like a dense sponge and keeps its shape perfectly one dry. We shape it into all sorts of supporting shapes.

Now, if you are willing to damage for fruits in the name of photography, I would add a toothpick with one end in the fruit and the other in the modeling magic for greater stability and precision.

Model Magic is what we use for seashells. It should easily work for fruits which already have lower center of gravity usually. Its a very maleable but dries into something like a dense sponge and keeps its shape perfectly one dry. We shape it into all sorts of supporting shapes.

Now, if you are willing to damage for fruits in the name of photography, I would add a toothpick with one end in the fruit and the other in the modeling magic for greater stability and precision.