Watermelon

One serving of Watermelon — 1 cup cubes (200 g) — comes to 40 kcal, 1.2 g protein, 7.8 g carbs and 0.4 g fat. Scaled to 100 g it works out to 20 kcal and 0.6 g protein, which makes it not a meaningful protein source on its own for a fruit item. That single serving is about 2.7% of a 1,500 kcal day and 2% of a 2,000 kcal day, so it's more of a filler than a target-hitter on protein without much extra planning.

Walking off Watermelon takes roughly 1,000 steps, using the rough approximation of 0.04 kcal burned per step (a population-average estimate for a moderate walking pace, not a personalised number). At ₹6 a serving it costs about ₹100 for every 20 g of protein it delivers, which is a mid-to-high price for protein compared with dal, eggs or soya chunks. It fits nearly every Indian diet type, including vegetarian, Jain, vegan. It's typically eaten at the evening snack slot. It's commonly eaten on fasting days (Navratri/Ekadashi-style).

If you want variety without changing the macros much, the closest swaps in the fruit category are Apple, Banana, Fresh coconut (malai), Dates (khajoor) — each keeps a similar role on the plate while shifting the exact protein-to-carb balance a little.