Like every Region before it, The Alola Region contains Pokemon in the wild that can actually be found holding items. Actually, there are more than 100 different Pokemon Species in the wild that can be found holding an item! That being said, most Wild Pokemon that can be found holding an item only have a mere 5% chance of holding said item. This means you may never come across Wild Pokemon that is holding an item!
You can always check to see if a Wild Pokemon is holding an item by having a Pokemon with the move of Thief. If your Pokemon knows said move and isn't holding an item, they can use it on a Wild Pokemon to steal the item they are holding. However, if they aren't holding an item, you will get nothing at all. If you don't have a Pokemon with the move Thief, you can always discover if a Wild Pokemon is holding an item by merely catching it and checking its profile.