Around 24 hours either way. Pour boiling water in at 8 am; it'll still be tea-temperature warm at 8 am the next day. Pour ice water in; it'll still be cold the following morning.

A sleeve. The bottle's structure is stainless steel — that's what holds the liquid and does the insulation. The bamboo wraps the outside as a natural-look exterior. The advantage: the steel does the food-safety work; the bamboo gives it the warm look and feel.

[[Bamboo Bottle]] (₹899, 12 hours): everyday work-day flask. [[Bamboo Vacuum Flask]] (this one, ₹1,399, 24 hours): longer hold, slightly larger, taller form factor. If your day is 8 hours and you refill from a tap, the Bamboo Bottle's 12-hour hold is plenty. If you travel, trek, or go a full 16+ hours between refills, the Vacuum Flask is built for it.

No — the steel cap seals tight. Built for travel and commute use. As with any flask, store upright when full to be safe.

Yes. The interior and the cap are both food-grade stainless steel — no plastic in the liquid-contact zone. BPA-free, non-toxic, rust-free.

Hand-wash the steel interior with mild soap and warm water. Wipe the bamboo sleeve with a damp cloth — don't soak it, don't put it in the dishwasher. The bamboo wrap doesn't love prolonged moisture.