Black coffee (no sugar)

One serving of Black coffee (no sugar) — 1 cup (150 ml) — comes to 3 kcal, 0.3 g protein, 0.5 g carbs and 0 g fat. Scaled to 100 g it works out to 2 kcal and 0.2 g protein, which makes it not a meaningful protein source on its own for a beverage item. That single serving is about 0.2% of a 1,500 kcal day and 0.2% 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 Black coffee (no sugar) takes roughly 75 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 ₹3 a serving it costs about ₹200 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 works at breakfast and 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 beverage category are Tender coconut water, Cold drink (cola/soda, regular), Diet / zero-sugar cola, Energy drink (Red Bull type) — each keeps a similar role on the plate while shifting the exact protein-to-carb balance a little.