While it may not come as a surprise, but in head to head testing, the best way to get over afternoon sleepiness was to take a nap. It works better than caffeine and it works better than getting more rest at night. Much of the Mediterranean world figured this out hundreds of years ago, but grabbing 20 minutes sleep at your desk is the sort of thing that gets you talked about in all sorts of career limiting kinds of ways. But it's what our bodies do naturally and it's what will make us more productive in the long run, so why does our culture so strongly rebel against this? It's not an every day thing, but every now and again, I get the overwhelming afternoon sleepies and I'd love to be able to just have a space to go and just take that little nap and be back to productivity rather than fighting it for the next two or three hours.