Short answer: During Paryushan, Jains follow a very simple, ahimsa-centered diet. Anything that causes more injury to tiny life-forms or involves fermentation is avoided. What remains is plain, sattvik, easily-digestible food taken only in daylight.

Common prohibitions (both traditions)

• No eating after sunset; eat only in daylight.
• Only boiled and filtered water, and only during fixed daylight hours.
• No root vegetables (kand-mool): potato, onion, garlic, carrot, beet, radish, ginger, turmeric (fresh or powdered), sweet potato, yam, etc.
• No green leafy vegetables (hari bhaji/saag) during the festival days.
• No fermentation or live cultures: no curd/yogurt, buttermilk, kefir, cheese, paneer, idli-dosa batter, yeast/bread, vinegar, pickles made by fermentation, etc.
• No honey, alcohol, or anything with eggs/meat/fish (these are anyway avoided in Jainism).
• Avoid sprouts, mushrooms, and foods likely to harbor many subtle beings (negligible/uncertain life-forms are given benefit of doubt by abstaining).
• Minimize fresh cutting/cooking; keep meals very simple and limited in number (ekasana/beyasana as per vow).

Generally allowed foods (simple, non-root, non-fermented)

• Grains and flours: rice, wheat, millet (jowar, bajra), semolina, poha, etc.
• Pulses and dals: moong, toor, chana, urad, masoor, etc. (not sprouted).
• Non-root, non-leafy vegetables: gourds and pumpkins (bottle gourd, ash gourd, ridge gourd, tinda, pumpkin), tomatoes, cucumber, capsicum, okra, eggplant, etc. (avoid any leafy parts).
• Fruits: normally permitted; choose clean, uninfested fruits; cut fresh and eat promptly.
• Fats and seasonings: ghee and plant oils; rock salt/sea salt; cumin, coriander seeds (not fresh leaves), black pepper, cloves, cinnamon, cardamom, asafoetida (hing), etc. (avoid root-derived spices like ginger/turmeric).
• Sweeteners: sugar, jaggery (gur).
• Milk is generally allowed; many households avoid all fermented milk products (curd, buttermilk) and also avoid paneer/cheese during Paryushan to keep the vrata stricter.

Tradition-specific notes

• Shvetāmbara Paryushan (8 days): strong emphasis on no green leafy vegetables for all days, along with the other rules above; many observe ekasana/boiled-food-only on chosen days.
• Digambara Das Lakshan (10 days): the same spirit of austerity; no-kand and no-leafy practice is followed strictly; many take an even simpler “boiled food” or “parna only once” discipline according to their vows.
• Local sangh practices may differ slightly; always follow the guidance of your guru and your declared vrata.

Essence

• Keep it minimal, non-violent, and pure.
• Eat less, only in daylight, and avoid roots, leaves, and fermentation.
• Focus the saved time and energy on pratikraman, svadhyaya, dhyana, and forgiveness.

If you wish to read an easy overview of Paryushan discipline and food do’s/don’ts, you can refer here: