One plastic bottle shouldn’t be refilled with water twice nor several times. The reason is that: A bottle itself is nest of germs and bacteria.
During the summer, bacteria are spreading around, so special attention should be put on the cutlery, as well as the glasses, bottles etc. The most dangerous part of the plastic bottles is the part that we put on our lips and it contains a lot of germs and bacteria that we insert in our mouth.
They are for one use only!
These bottles are for one use only and the ones, which are meant for several uses have description on their wrapping. Instead of filling the bottle with bacteria, change it after one usage.