As others have said, there's no such thing as cycled water unless your fish store is defining the term 'cycle' in a significantly different way than what people on this forum mean when they use the term.
A 'cycle' in it's purest sense is a predictable and sequential rise and fall in concentration of various species of nitrogen ions over a period of time, starting with ammonia, ending with ever increasing levels of nitrate. It's the measurable chemical result of a biological process that we can't easily directly test: the establishment of a community of several kinds of nitrifying bacteria in response to the presence of a source of ammonia. The end result of the cycling process is a bed (note the term bed, they're substrate bound) of bacteria that remove ammonia and nitrite from the water column, and contribute nitrate to the water column. So if by cycled they mean that they sold you some water with high nitrates, then yes, this is a possible thing to buy I suppose (though not sure why you would want that). However, just like you wouldn't wear an olympic athlete's sweaty workout clothes and expect to somehow get fit, you shouldn't expect to use the water from a cycled tank and expect that to have any impact on whether or not your tank will see sequential spikes in ammonia, nitrite, and then nitrate in response to the initial addition waste producing animals or organic matter. The 'work' doesn't take place in the water, the symptoms of the work done on a substrate are measurable in the water. There's a large and significant difference. I'm not saying you or others who have done this will or will not have a detectable nitrogen cycle, what I am saying is that this will not be one of the factors that contributes to it.
What is in the water from a fish store is potentially all sorts of parasitic protozoans, aiptasia planula, high nutrients, and questionable parameters. I go to great lengths to prevent even a single drop of fish store water from getting in to my tank for that very reason.