Short answer: No. Vomiting by itself does not break a Jain fast.

Details and care to take

• In both Digambar and Shwetambar practice, a fast is considered broken by intentional intake (eating/drinking). Vomiting is expelling, not intake, so the fast remains intact.
• If any vomited material reaches the mouth and you swallow it back, that is counted as eating and the fast is broken.
• After vomiting, rinse your mouth thoroughly and spit everything out. Do not swallow even small amounts.
• If you are unwell, it is acceptable to end or modify the fast (e.g., take aushadhi/medicine with proper pachchakkhan). Health takes precedence; breaking due to genuine illness is not a fault.

Essence: Expulsion does not spoil the fast; re-swallowing does. Maintain care (samiti) after vomiting to avoid any inadvertent intake.