You can go to https://www.twilio.com/login/password and enter a fake email address and repeated fake passwords. Or one of the addresses listed here: https://github.com/dessant/buster/issues/178 Though I got pretty easy ones trying it.

twilio site actually prompts a captcha after a few unsuccessful login tries but it just says "Pick any square". I've tried a few times and clicking any of the 6 options underneath work lol.