Brushing your teeth RIGHT after eating is never a good idea. In this case, it was a spectacularly bad idea. Eating and drinking so quickly, I had to burp. I was midst tooth-brushing when I did so. The burp turned into one of those "throw up in the back of your mouth" things. Which of course I then tried to swallow, but had a mouth full of toothpaste and toothbrush, and so didn't close my mouth completely.
I thought tooth-paste and orange juice was disgusting together - I promise, tooth-paste and vomit is infinitely worse.