They've adopted Uber's contract worker model -- and now, they're fighting the same legal battles.

Three on-demand food delivery companies -- GrubHub (GRUB), DoorDash and Caviar -- were hit with lawsuits Wednesday in a San Francisco Superior Court.

The suits allege that the firms are improperly classifying workers as independent contractors while treating them as employees. Workers must pay for expenses like gas, parking fees and phone data, which would be illegal under California law if they were classified as employees.

Attorney Shannon Liss-Riordan says these companies are skirting the rules by using improper worker classifications.

Liss-Riordan is the attorney for all three new cases and is also representing similar cases against Uber and at least seven other on-demand companies.

"They've all seen Uber do it and become so wildly successful that they think it's OK," said Liss-Riordan, who is based in Boston. "[They're] trying to use the excuse that there's something new and different -- the so-called 'on demand economy' -- and that they're somehow licensed to ignore the wage laws."

GrubHub -- which went public in April 2014 -- hires contract workers to deliver food ordered from restaurants that may not have their own delivery services.

One driver, Andrew Tan, alleges that his pay as a GrubHub worker fell below California's minimum wage during many weeks because of the costs of fuel and vehicle maintenance. When Tan worked overtime, he wasn't compensated with overtime pay.