Twitter sprints?

You mean, call in a writing sprint? Former Buffy and current Once Upon a Time writer Jane Espenson does that.

Since she's also usually delightful and fun to read, I can safely recommend following her.

There are a few accounts that are around solely to host sprints. @Getwordies holds sprints on a regular basis and has a set schedule.

On Fridays, @frinightwrites holds them through the whole day. Sometimes they lead other days of the week, but I haven't seen that happening as much since NaNoWriMo ended.

Between these two there's a lot of time covered, but there are a few other people around who hold sprints on a less scheduled basis that you'll find if you check out the #wordsprint hashtag every now and again