For vegans: Moong sprouts and sprouted ragi and amaranth (millet from Gujarat) are nutritionally dense foods. Include some legumes like red kidney beans or red channa and chickpea. This can make the meal filling. Eating any two seasonal vegetables can all fit into a Rs 100. Root vegetables like carrots or turnip or sweet potato, either baked or boiled and with healthy fats like coconut oil, can balance the meal.
For vegetarians: Include a bowl of yogurt, raita, buttermilk or its counterpart whey water. This adds to the protein content. Using homemade fresh paneer with jowar or bajra rotis and seasonal vegetables make the meal affordable.
Non-vegetarians: Fish is a viable and reasonable protein option: choose higher fat varieties like cod. They are healthier poached or steamed. Add brown rice (which can be cheaper than white rice) and a mixed vegetarian soup or curry. Eggs can be a daily cheap source or protein that can fit into any budget. Two vegetables, one protein with some whole grains is a good balance and well within the budget of Rs 100.