When Flanders is about to take his 'sleep aid', the perspective changes to a close-up of a half-full glass of milk next to a box of Graham Crackers and a carton of milk. Later, when Flanders wakes from his personal Hell dream and picks up his Bible, the milk carton is nowhere to be seen and the glass is inexplicably full (Note that Flanders went to sleep almost instantly after drinking his milk, so it's unlikely that he filled the glass himself).
Homer says twice he didn't know that Flanders was left handed, although he knew it since Flanders opened the shop for left-handed.