What are those buttons on soft drink lids for?

Question

...the ones that say diet, coke, other, etc.

Answer 1

So that when you order several drinks you will know which one is which. The server is supposed to push in the appropriate 'buttons'

Answer 2

You push one down to indicate what is in the drink.

In the golden olden days, when the fast food employee actually made the drinks for you, they could mash down the buttons so that when your family/friends all got their drinks everyone know what was in each cup.

Now, it is useful to do you own if your friends/family might get them mixed up on the table or at home.

Answer 3

You order two different sodas at the drive thru. One is Diet Coke, one is just regular Coke.

When you get the sodas from the drive thru person who pushes them in, you look at the buttons to see which one is which, which makes for less confusion when trying to figure out identical sodas.  

Answer 4

some are for identifying the beverage, but one of them is the "Eject" button. Be careful not to push this one...  

Answer 5

so you know which one is which, or so you can just press them  (: