Interesting question. I think it's wrong to think of it as a fallacy.
In economics they use scarcity value, as a way to think about how relative available affects our sense of what things are worth. It can also be looked at in social psychology.
You can think of the candies or biscuits as having value in terms of certain pleasurable sensations over time, and that really to maximise the pleasure we should eat them one at a time, slowly. But while we have plenty we may prefer a short term strategy, immediate over long term pleasure.
There is also a social transaction value. Being able to offer other people candies or biscuits, can maintain your reputation as a good host, can leave others in your debt. To add to the last candy with new ones requires some effort, attention, and cost. In our time of plenty we tend to ignore the risk there won't be more, but it's real. Imagine how a British person likely felt about how they valued their food just before WW2, vs in the rationing era that lasted until 1955. Many treats and luxuries were unwittingly eaten for the last time in a long time. We could have a supervolcano, or nuclear war. Or a food crisis when the worlds largest grain exporter can't get grain out (used to make glucose), and energy prices spike - currently we may be insulated from this, but price rises are coming. Risk and hazard are involved in assessing value, anyway.
I find it interesting that we don't really have the category of 'miser' any more, and we could unpick why. 'Hoarders' seem to have a problematic relationship towards not keeping access to resources. Being able to choose delayed gratification, often measured with candies, is seen as a key child-development marker.
Conversely there is Zen parable, about being chased off a cliff by a tiger and hanging on by a vine that is fraying - if you see a wild strawberry then, appreciate it's sweetness. Because we are always beset by troubles, but even so we can appreciate simple momentary pleasures. Unless someone else already ate the last one..