I love these but I think ive done something wrong because they all seem to just have the same items ore are they meant to all be the same and its just for decorative purposes?

Hi
As you can see in the description, all the coffee stand are recolors of the university coffee stand. A recolor mean that you change the way it looks, the texture not the program. That also mean that they sell the same things than the original one does because the program is the same.
So you did nothing wrong, this is totally normal that they all sell the same food an drinks.
If instead you can only buy vegetables, it's a bug (a conflict with others mods in your computer).

Hope I answered your question, have a great day