I constantly feel tired after work. How do I get energized again for a productive evening?
Before you can effectively re-energize after work, you need to first determine what is contributing to your fatigue. Look at:
- how long your work day is
- how physically active are you during your work day
- body mechanics at work
- what and how much you eat while at work
- what your stress level is like
- how well you are sleeping
- having your doctor assess you for fatigue-related conditions such as anemia
The idea here is that if you maximize your energy throughout the day, you’ll have more of at the end of the day when you want to be active in other ways.
You may not be able to modify the length of your work day, but, if you can, try not to work overtime every day. We are often at our most efficient just before going on vacation – think about how you can sustain that level of efficiency on an ongoing basis so you can avoid putting in extra hours. 
If your job requires you to be seated for long periods, try to get up and move for 5 minutes out of every hour. Have a short break to stretch and take some deep breaths. Drink some water (dehydration is a common cause of fatigue). 
Whether you are seated or moving during your work day, make sure you are using good body mechanics. Poor posture generates muscle strain, which can be fatiguing. 
Diets that provide more calories than nutrition can sap your energy. A low glycemic diet of whole foods will sustain your energy and minimize the brain fog that can accompany fluctuations in blood sugar. Make sure you spread your calories throughout the day – this means eating 3 meals each day with, or without, snacks. 
Most jobs involve some stress, which can be positive or negative. Positive stress feels exciting and motivating but can lead to pushing yourself too hard. Negative stress feels oppressive and intimidating; it drains you because you emotionally resist your circumstances. Proactively managing your stress can put you in the “sweet spot” where you feel engaged and satisfied with what you are doing. Regular movement or exercise can help you deal with the effects of stress better. 
If you start your day feeling unrefreshed, it will be difficult to end it feeling energized. The “I’ll sleep when I’m dead” notion that some people have may become a self-fulfilling prophecy as sleep deficiency and sleep disorders can contribute significantly to poor health. Do everything you can to promote good quality sleep in sufficient quantity. A short nap (30 minutes or less) after work can lift your energy. 
- get a good night’s sleep and nap if you need to;
- drink lots of water;
- eat a healthy diet;
- move a little more – go for a walk or a workout – and pay attention to body mechanics;
- take several deep breaths throughout the day;
- don’t overwork, and proactively manage your stress.
If you keep your energy supply topped up throughout the day, you’ll find you’ll have all you need at the end of the day.
 How to Be More Efficient at Work
 Deskercise! 33 Smart Ways to Exercise at Work
 Proper Body Mechanics at Work and Home
 Free Low Glycemic Diet Plan | LIVESTRONG.COM
 Healthy Sleep
This article originally appeared as an answer on Quora.