I've tended to find with experimentation that adjusting your nap duration can stop that wasted effect. I tend to take a 90 minute lunch break, where i nap. It takes me ages to get to sleep, but I'm rarely wasted (even more tired when i wake up ). I suspect i get somewhere between 20 and 60 minutes sleep in total, but 9 times out of 10 I'm refreshed. The other 1/10 its generally my work brain won't stop considering ways to resolve work issues.