The internet is only just learning what the little buttons on the lids of McDonald's drinks are for - and no, it's not just for fun.
Many were surprised to learn it actually acts as a labelling system. 'Diet', 'Tea', and 'Cola', are just some of the buttons you can press, and it helps customers decipher which drink is which, instead of doing the 'taste test' to work out which Coca Cola is diet and which isn't.
The lids also have a rectangular button, which can be pressed if a mistake is made, causing the other buttons to reset.
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