You could make use of a variable to achieve this. So for example, on your buttons you would have something like this:
ButtonA - OnSelect : Set(listFilter, "fruit")
ButtonB - OnSelect: Set(listFilter, "vegetable")
Then on your screen 2 dropdown, set the Items property to something like the following formula:
Filter(sharePointList, yourColumn = listFilter)
Now you kind of mentioned in your posting that "The data for fruit and vegetables are stored in the same table in a sharepoint lookup." Does this imply that the column you are looking at in your SharePoint list is a Lookup type column? If so, then adjust the formula above to the following:
There are some delegation issues with the above if that is a concern with your list sizes. If not, then you can ignore them. If so, then other steps would be needed to resolve that.
I hope this is clear and helpful for you.
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