The best alternatives to Twenty Tables are Bitebot, Down To Lunch, and /Lunchbox. If these 3 options don't work for you, we've listed a few more alternatives below.
Bitebot is a bot for Slack that not only helps you coordinate everyday lunches, but also split and track payments between all team members. You don't need to pay your coworkers back every time you eat together - Bitebot will know when it's your turn to pick up the tab.