My understanding was that Beit HaOtzar keeps the coin (and maybe later causes it to be destroyed), meaning there is tracking of that coin since it may not be used.
For someone who tithes only as a one-time thing, there's a reasonable chance he will forget and use that coin at some point.
Is there an option to transfer the sanctity from the coin onto a fruit and then put it in a bag and throw it away, so that the coin can then be used again?
Thanks

Strictly speaking, you cannot transfer the coin onto fruit, because the coin is forbidden for benefit by impure people. But you can transfer the coin onto food worth a perutah and destroy it (according to the law, it is forbidden to destroy coins).
I'm copying here note 7 from Peninei Halakha (http://ph.yhb.org.il/07-12-10/), which is relevant to our case:

For example, if one set aside a one-shekel coin for this purpose, he could redeem onto it about twenty times, based on the calculation that a perutah is approximately five agorot. And after redeeming twenty times, he can transfer all twenty perutot in the shekel onto one perutah in another coin. The best method is to designate two coins, one of five shekels and one of one shekel (I usually tape them together with Scotch tape so they are marked), and always redeem onto a perutah in the larger coin; and every so often, transfer all the perutot in the larger coin onto one perutah in the smaller coin. After that, transfer all the perutot in the smaller coin onto one perutah in the larger coin, and in this way one can continue redeeming onto the designated coins again and again. And even if he has family members or friends for whom it would be difficult to keep a coin in a protected drawer, he can give them permission to redeem onto a perutah in his larger coin, and be careful every few months to reduce all the perutot back to one perutah. Twice in the seven-year cycle, that perutah must be destroyed: on the eve of Passover in the fourth year, and on the eve of Passover in the Sabbatical year. And this is how it can be done: take a spoonful of sugar, stand by the sink, and say: "All the perutot in my coins are transferred onto the sugar in the spoon" (which is worth a perutah), and run water over the sugar, thereby destroying it.

A. They have in their coins a "severe perutah," which is needed when redeeming second tithe that is not worth a perutah.

B. They have an arrangement for giving the poor tithe, by means of an advance loan to a poor person from which they deduct at each separation of poor tithe.

Best regards, S.Z. Levinger

Indeed, that's correct. I should have added that one must make sure to have a severe perutah. Here is its description:

The Sages established that one may not redeem second tithe that is not worth a perutah unless the coin onto which he is now redeeming had already previously had second tithe worth a perutah redeemed onto it. Therefore, one must make sure that the first redemption done onto the coin is for an amount worth a perutah.
Since tithes have different levels of obligation—for example, a person who grows fruit in his own field has a more stringent level of obligation than a person who buys in a store; and the level of obligation for grain, wine, and oil—that is, wheat, wine, and oil—is more stringent than the level of obligation for other fruits and vegetables—therefore one cannot redeem second tithe worth less than a perutah, at a higher level of obligation, onto a coin whose first redemption was of second tithe at a lower level.
Therefore, when designating a coin for redeeming second tithe, one should redeem onto it the first time the most stringent level of second tithe—namely, second tithe worth a perutah, grown in his own possession and not purchased, consisting of grain, wine, and oil, and whose processing was completed with the intention of eating it.