Fruits are the means by which flowering plants disseminate seeds, and the presence of seeds indicates that a structure is most likely a fruit, though not all seeds come from fruits. Most fruit found after the Great War has been infected with the radiation of the wasteland, and passes on a few rads to anyone that consumes it.
A strange piece of fruit that appears to be an apple. No preservatives and no additional food coloring added. This fruit has been infected with the radiation of the wasteland, and passes on a few rads to anyone that consumes it.
In Fallout 2, fruit can be used to make super stimpaks. Myron can be recruited into the party, and with 76% or more Science skill, the Chosen One can ask Myron to make super stimpaks: the recipe is fruit + Nuka-Cola + stimpak. Each one takes a little time to make; a good way to kill time while waiting for shops to open, or healing skills to reset, etc.
The apple version can be seen in Fallout and Fallout 2, and the pear version can be seen in Fallout Tactics.