notepad++

https://thomas.vanhoutte.be/miniblog/notepad-remove-new-line-and-add-comma/

and you want this outcome:

Apple, Orange, Strawberry, Banana, Kiwi

Then do this: CTRL + H to open the Replace window. Then select Regular Expression in Search Mode. In the Find What, enter [\r\n]+. Then in the Replace with, enter the comma (,) and maybe followed by a space if you also want to add that.