Afternoon Sleepy. Because of a natural rhythm in our body's systems, it is common to feel a little tired in the mid- to late afternoon. Best thing to do is to be physically active during this time. If you work at a desk, get up, run errands, visit with co-workers, make deliveries. This physical activity will help you from feeling so tired and there are no chemicals involved. Best of both worlds.
Tough. Mid-afternoon sleepiness is experienced to some degree by everyone. The natural circadian rhythm that maintains or wakeful state take a dip in the early afternoon. Some are bothered by it more than others. That with the post-prandial "tide" after eating can make it tough to not feel tired in the early afternoon. Trying to do some light exercise or decreasing carb content during lunch may help.