It is normal that the water cup is not packaged. Not even when I bought it.
Hot water can be stored. Compared with other brands, buckles are relatively insulated, but think about it. After all, polyethylene has a heat preservation effect, but it is not as good as a real thermos cup, and it will gradually cool down after a long time.
The sealing is very good.
In the supermarket, I saw containers such as water cups, oil pots and cups without packaging and instructions. Only the box is wrapped in plastic paper. What you bought should be fine.