Making liquor-soaked cherries for Manhattans
There are several ways to make them. You can start either with high quality candied or dried cherries. Or you can use decent canned or preserved cherries. There are some excellent ones from Europe available. Which type you use is up to you. candied ones give you something firm, dried ones are in the middle, and canned ones a bit soft. Go for the darkest and least sweet cherry you can find. I think they end up tasting better than really sweet or light ones.
Then soak them in your booze of choice for anywhere from several days to weeks. You can keep them soaking forever and as long as they are covered with alcohol they not only stay fine but improve. They don't need to be kept cool unless you use a low alcohol product like vermouth. Then they are best kept refrigerated.
You can also make them from scratch by candying the cherries yourself in a mix of water, a decent booze, and sugar that you make into a syrup, and then simmer the cherries in it for an hour or more and then let cool in the liquid.
I have made them with several types of alcohol, both straight and a mix. Some that turned out real well were vermouth, rum, bourbon, smoky single malt, various liqueurs like amaretto, Drambuie, Grand Marnier, etc.
Tupperware is ok, but a glass jar is better. You can use any clean jar that you have lying around, just make sure it is really clean.
By the way, Luxardo, who make the Maraschino liqueur also make cherries. They are very expensive, but mighty tasty. I pour out the syrup and save to use in cocktails and add a nice aged rum to cover. They just keep on getting better. Last night I even used a few in my gin on ice and it made an amazing drink.
My technique (learned on this board): use sour cherries only, fresh when you can get them (wash them first), dried otherwise. The dried won't look quite as nice, though they will plump up some. Store them in a lidded jar in the fridge, covered with some naked (unsugared, unwatered) distilled spirit: I have used brandy and Maraschino liqueur at different times to good effect. A week or so of maceration is all you need.