Kanchipuram is a conservative temple town and food here is overwhelmingly South Indian vegetarian. That is not a limitation: Tamil vegetarian cuisine at its best is deeply satisfying, and Kanchipuram is an honest place to eat it.
The staple is the Tamil Nadu thali — a large steel plate with rice at the centre, surrounded by sambar (lentil and tamarind soup), rasam (thinner and pepper-sharp), several vegetable curries, curd, and papad. It is refilled as many times as you ask. Lunch is the main meal; most thali restaurants serve it between noon and 3pm.
Breakfast is equally serious. Kanchipuram has its own local idli variant — the Kanchipuram idli, spiced with black pepper, cumin, ginger, and sesame oil, denser and more flavourful than the plain hotel idli — traditionally offered as temple prasadam at the Varadaraja Perumal Temple. Dosas, vadas, and upma round out the morning options. A tumbler of South Indian filter coffee is the essential accompaniment to all of it.
Most restaurants in town are simple, clean, and cheap. There is very little in the way of non-vegetarian food, and no meaningful bar culture.