Also a good way to determine if someone has eaten fish or tomatoes recently.
Tat: Yeah, here you go.
Soph: Is that backwash at the bottom?
Soph: You keep it.
(incidentally, if anyone gets a bottle with backwash in the bottom, try refilling it with its original liquid as well, so it's full, then heating the bottle from below. Because it's seperate, I wonder if it behaves like a lava lamp. If anyone wants to try this, feel free to enlighten me.)
When multiple people drink from the same container, there will usually be some amount of backwash put back into the container; as the number of sips increases, in general, the concentration of backwash also increases.
Sven- "Just some backwash of water chestnut and sesame"
William- "Why on gods green earth were you eating water chestnuts and sesame seeds?"
Sven- "I.. dont.. know..."