Wouldn't milk bottles have blue caps? One of the replies of the tweet says they're bleach, not milk.
Around where I live, the color of a milk bottle's cap varies depending on the fat content--red for whole milk, blue for 2-percent, and so on. I think green is 1-percent.
Where Teto lives, who knows?
Anyway, if it's bleach that's fine, although it only raises different questions. :)