Did you get it right?
The porch table is ready except for one common iced-tea garnish.

The Answer
The missing object is a lemon wedge.
Here is why
- Scan the iced tea glasses.
- Look for any lemon slice or wedge.
- There is no lemon wedge anywhere in the scene.
Why people miss it
The table has plenty of lunch items, which distracts from the missing garnish.
Did this one fool you at first glance?