In Varshitap, brahmacharya (celibacy) is strongly expected for the full period of the vow (about 13 months), not only on some days.

Very simply:

• Varshitap is not just a food‑fast; it is a full discipline of mind, speech and body.
• For shravak–shravika (lay people):

- During any major tapa (Upvas, Ayambil, Masaksaman, Varshitap, etc.) Jain acharyas clearly say: no sexual activity at all, even with one’s own spouse, for the duration you have taken that tapa. ( jainknowledge.com)

• So if you take Varshitap as a 13‑month vow, the ideal and traditional maryada is:

> Observe complete brahmacharya for the entire Varshitap period.

Why?

• Sex increases raag–dvesh, kashaya and vishaya‑asakti (passion and sense‑indulgence).
• Tapasya’s goal is to burn karma and calm passions, so sexual activity directly goes against the purpose of Varshitap.

Digambar & Shwetambar:

• Both accept that tapasya and brahmacharya go together.
• Digambar: even stricter about brahmacharya in all higher tapas.
• Shwetambar: in Varshitap, Paushadh, etc. one is told to live “like a sadhu for that period”, which includes celibacy. ( jainknowledge.com)

In practice, you should:

• Take the Varshitap with clear sankalp:

- alternate‑day fasting as prescribed, plus - continuous brahmacharya till Parna on Akshaya Tritiya.

• Do this only under guidance of your guru / local Jain sadhu‑sadhvi.

You can read a simple Varshitap‑vidhi explanation here