We know that it can be frustrating to have a balance left on the card that you feel you cannot use. There are a few ways that you can use up that final balance to ensure you are not left with dust amounts on the card.
In most major supermarkets, you can make partial payments with cards, meaning that you can use the card to pay for lower value items without the merchant requiring any minimum spend in order to do so. This will require you adding the card to Apple Pay in order to do so.
In addition to major supermarkets, you may be able to make partial payments at other types of merchants:
Gas Stations: Please note that this is referring to paying in-store at the POS in gas stations, the cards will likely be declined if you try to pre-pay using the machines. This may be dependent on the country you are in and the particular gas station. Confirm with the cashier first.
Major retailers: Similar to major supermarkets, most major retailers should be able to allow you to make a partial payment using two different cards. It again may be dependent on the country you are in and the Point-of-Sale terminal of the retailer, but this may be a viable option for you.
Additionally, some online services will allow you to load a specific amount to your account balance from a card:
Amazon: You can load a specific amount (usually 5$/5€ minimum) to your account balance from cards. Please note that this may have privacy consequences loading the card on an account connected to your address and name. For Amazon US, you can do so here.
Finally, if you so wish, there are a number of non-profit organisations which a number of customers have previously donated to, in order to use up the final amounts on their cards. Some of these organisations are Wikipedia, VLC, Linux Foundation.
Note: For International cards, where the transaction is in a foreign currency, it is important to remember that due to FX charges (around 2%), you must account for this in the amount you are partially paying/loading on the relevant account.