You'd need to compile a list of all the possible permutations, and list them as options in the "When I say" field.
For the example of three items, that's doable, E.G. using
this calculator (which, unfortunately, does not allow spaces, though you could substitute underscores and replace them later on)
You'd want the permutations for three items, two items, and a single item, which when combined result in
apples
oranges
bananas
apples, oranges
apples, bananas
oranges, apples
oranges, bananas
bananas, apples
bananas, oranges
apples, oranges, bananas
apples, bananas, oranges
oranges, apples, bananas
oranges, bananas, apples
bananas, apples, oranges
bananas, oranges, apples
A text editor with a robust find and replace feature (E.G. Notepad++) can then be used to turn this into a list of command phrases, with the proper separators:
apples;oranges;bananas;apples oranges;apples bananas;oranges apples;oranges bananas;bananas apples;bananas oranges;apples oranges bananas;apples bananas oranges;oranges apples bananas;oranges bananas apples;bananas apples oranges;bananas oranges apples
This result is achieved by replace "\r\n" with ";" (with the search mode set to extended in Notepad++), and replacing "," with "" (blank) to remove the commas (this step can be optional)
Copying the list the linked website outputs adds " " in front of each entry, which can also be removed using find/replace in this manner.
If you want to add "and" for the last item, you'd need to use a regular expression, like this:
(?!.+ )
(making sure to set the search mode to regular expression)
replacing with " and " (note the spaces wrapping the word)
Run that replace first, before the others (it can technically be done after replacing the commas, but not after replacing the newline characters, however you might as well do it first)
Running all three would result in
apples;oranges;bananas;apples and oranges;apples and bananas;oranges and apples;oranges and bananas;bananas and apples;bananas and oranges;apples oranges and bananas;apples bananas and oranges;oranges apples and bananas;oranges bananas and apples;bananas apples and oranges;bananas oranges and apples
Notepad++ does allow you to record macro sequences, so the steps could be automated.
Do note that adding more items rapidly increases the amount of permutations, and thus the phrases that must be passed to the speech recognition engine.
E.G. the three items in the example result in 15 phrases, but adding a fourth increases the total to 64 phrases.
Adding even a single optional dynamic command section, E.G. "[do this;do that]", doubles the input item count to eight, however the output shoots up to well over 100000 phrases, which the online tools I could find won't output.
Generating all the variations ahead of time as shown could be simpler than trying to determine which combinations of dynamic sections generate which combinations.
If you are going to use the latter technique,
this command could be useful to visualize what will be generated.
The exponential increase in possible phrases should be kept in mind regardless, as at a certain point profile loading times will get quite long (depending on your hardware), and in more extreme cases, VoiceAttack (or the speech recognition engine itself, in the 64bit version) will run out of memory.