The particular problem here is there's no feedback as to why you boycott them.
You see, the following headline has more effect on CEO's and decision makers
"McD's sales drop 10% after customers refuse the app and other forms of spying" --Forbes
If it's a silent boycott then you see stupid headlines like
"Are millennials killing McD?"
Remember the entire purpose isn't so that one company doesn't track you with an app, is so every company figures out tracking you with an app is a bad idea.
So write to the news. The problem is not lack of publicity avenue, it's too few people seem to care enough about apps selling their data to make the headlines in the first place. They'd rather just get the burger and not care.