The following works in SharePoint 2013, 2016 (beta 2) and SharePoint Online.
One of the common reasons to enable the Publishing Feature was to get the Navigation page so you could have dropdowns in the Top Link bar. Turns out that in 2013 and later you can do this without the Publishing Feature.
The trick is drag and drop. Starting with SharePoint 2013 you have an “EDIT LINKS” button on the page. (No Top Link Bar or Navigation page needed!)
When you click EDIT LINKS you can add a new item to the menu by clicking the (+) button.
Then there’s the trick! Drag the new link just under the parent link. (I’ll drag this one under the “Subsite1” link.)
Click Save and now you have dropdowns!
What you don’t get…
The Publishing feature Navigation page lets you select options like Open in New Window and Audience selection.
But if all you need are some dropdowns…