Even if it is voluntary charity, because giving charity from good and average quality fruit is better than giving charity from inferior fruit.

It is narrated from Sayyiduna Awf bin Malik Shuja'i رضي الله عنه that the Messenger of Allah صلى الله عليه وسلم came to the mosque and saw bunches of dates hanging. Among them was a bunch that was spoiled and of poor quality. He had a staff with him, and he struck that bunch with the staff (and the dates fell down), and said: "If the one giving charity had wished, he could have given better charity than this. Surely, the owner of this bunch will eat spoiled and poor-quality dates on the Day of Resurrection."