Quick reality check: you cannot boycott a business that you never supported in the first place. The only people who can successfully boycott Applebee's are their regular customers, and given that Applebee's targets conservative baby boomer middle manager types it's extremely unlikely that any boycott is going to happen.
We can, however, hurt Applebee's by directly attacking their ability to do business. Applebee's depends on a constant stream of low wage employees which must be constantly replenished. They operate on the assumption that everyone applying to work for them is doing so sincerely, and have sized their HR departments accordingly. If that were to change and they were unable to replenish their labor pool the entire system would seize up and break down, at which point we could use their corporate carcass as a warning to others: fuck with us and we will fuck with you back.
If you're really angry at applebee's, take a minute out of your day and apply to work there. Remember that your objective here is to waste their time – if you fill out every field with some variation of 'fuck you gas boy' you will waste maybe a second of someone's time, but if you fill it out so that you look like an experienced, desirable employee you could easily waste hours of their time. Take the process as far as you can – if you are offered an interview accept it, only to reschedule at the last minute and see how many times you can pull that off.
We actually have an opportunity here to retaliate in a way that they will feel – can we please, please not fuck it up? I know y'all are redditors and expecting anything from you is probably foolish of me, but really all you have to do is fill out a couple applications it's not that hard. Please?