When you’re dehydrated you get tired, so drink lots of water! Also, vitamin C is an energy booster. Some yoga poses can make you feel more energized as well. The only one I know of is when you lay on the floor and put your legs up a wall and just relax for 10-20 minutes, but I’m sure there are more. ^.^
I find that eating protein or oatmeal can help start me off with energy in the morning. But doing stuff like carrying some almonds with you for a mid-day snack might also help. I like pistachios and peanuts too.