To be fair, signalling doesn't require fine manipulation of a heavy object down between your legs and out of your line of sight
It's entertaining on fixed
The bottle on the down tube is OK, the one on the seat tube a little more tricky and the third one, down below the downtube and between the cranks, well, that's a bit of a bugger. MO is to swap them around as they empty; downtube one first, then swap that for the seat tube one, then finally for the under-the-seat-tube one.
I'm guilty of not drinking enough - anything like enough - and I often suffer for it.