Answer

After sunset, the usual Jain practice is to take Chauvihar Pachkhan if you are stopping all food and water until the next morning.

If you have done Ayambil, then after completing Ayambil you may take the appropriate Pachkhan depending on what you will observe after sunset:

• Chauvihar Pachkhan – if you will not take food or water after sunset.
• Tivihar Pachkhan – if water is allowed but no food is taken.

Regarding Panhar Pachkhan: Panhar Pachkhan is generally related to taking water. Whether you should take it after Ayambil depends on your tradition, local practice, and the guidance of your Guru/Maharaj Saheb/Sadhviji.

Explanation

In Jain Dharma, after sunset, eating is avoided because of the principle of minimizing himsa. Many shravaks and shravikas take Pachkhan to formally renounce food or both food and water for a fixed period.

Ayambil itself is a tapasya where one eats very simple, tasteless food once during the day, following specific rules. After Ayambil, the evening Pachkhan is still based on what you intend to renounce for the night.

Takeaway

If you are unsure, the safest and most traditional approach is to ask your Guru Bhagwant or local Jain elder, because Pachkhan wording and practice can vary by tradition. Generally, after sunset: no food and water → Chauvihar, no food but water allowed → Tivihar.