Answer

In Jain Dharma, what can be eaten on a tithi depends on which tithi observance or vrat you are following.

Explanation

Common possibilities are:

• Upvas: nothing is eaten.
• Partial fast: only simple, sattvic Jain food may be taken, depending on the vow.
• Ekasana: one meal only, in one sitting.
• Ayambil: very plain food, usually without oil, ghee, milk, sugar, fruits, sweets, or strong spices.

In general, during Jain observance, people avoid:

• root vegetables
• onion and garlic
• fried or rich food
• sweets
• non-vegetarian food
• alcohol

If your family or guru follows a specific tradition, that tradition’s rules should be followed exactly.

Spiritual Understanding

A tithi vow is not only about food. It is about:

• reducing इच्छा and attachment
• increasing discipline
• cleansing the mind
• deepening devotion and self-control

The simpler the food, the stronger the तपस्या and inner restraint.

Takeaway

If you mean tithi fast, the answer is: it depends on the type of vrat. For upvas, eat nothing. For partial observance, eat only what your Jain tradition allows.