Getting tired half way through the day is common. There could be a lot of reasons that drive us to this state. The lethargy can impact our work as well, making it important to avoid such a condition.
One way in which you can do this is by drinking more water. Staying hydrated is a proven way to keep you energetic and less lethargic throughout the day. Starting the day with a huge glass of water can bring some great results.
As water has zero calories, there need not be any concerns about how much you consume it. Drinking lots of water is also important for keeping your metabolism working properly throughout the day.