It is now confirmed, McDonalds was hacked.
http://wishtv.com/2017/03/16/mcdonalds-investigating-hack-after-tweet-calls-trump-disgusting-excuse-of-a-president/
Confirmed by whom? McDonalds? Sounds like corporate CYA to me.
Nobody hacked them. This has all the earmarks of an accidental tweet by the guy in charge of releasing tweets to the public.