You don't have to have a long workout to get a quick energy burst. In fact, simply performing one set of a given exercise can be enough to give you the energy burst you need to get you through the day. There are a host of traditional and modern workouts that are ideal candidates for quick and invigorating workouts, making it easy for you to find exercises that will best suit your fitness needs.

Pushups
Touch your chest to the floor for a proper pushup.

Pushups are a traditional yet effective workout. The advantage of pushups is that you don't need equipment to perform them and you can perform a challenging number of pushups in a short amount of time. To perform a pushup, place your hands shoulder width apart on the floor and extend your legs behind you so that only the tips of your toes touch the floor. Bring your chest to the floor, keeping your entire body as parallel to the floor as possible without arching your back. Taper the amount of sets and repetitions you perform to your own capabilities, keeping in mind that even five to 10 pushups can give you an effective energy burst.
Abdominal Crunches
Touching your elbows to your opposite knee is a variation of traditional crunches.

Abdominal crunches are another classic but essential workout. Like pushups, you can perform crunches virtually anywhere without any equipment. To perform crunches, lay with your back to the floor and your feet off the floor. Your knees should be bent at a 90-degree angle so that your lower legs are parallel with your torso. With your hands behind your head, bring your chin towards your knees, without moving your head or arms. Concentrate on isolating your abdominal muscles, using only them to perform a crunch. Perform three sets of at least 15 repetitions to get a quick energy burst.
Star Squats (See References 1)

Star squats are a great workout for their simplicity and comprehensive muscle isolation. Star squats help develop core body strength especially but also many muscles, such as the hamstrings, calves, lower back and triceps. To prepare for the star squat, you should squat down with your feet together and place your hands palm down on the floor at your sides, directly below your shoulders. With a burst of energy, kick your feet behind you so that you land in the same position in which you would start a pushup. Repeat at least 10 times or until you get tired.
Jumping Jacks
Jumping jacks target many muscles in the body.

Jumping jacks are a simple exercise that you can perform, regardless of your fitness level. Stand with your feet together and your arms at your sides. All in one motion, jump and extend your feet to your sides as you simultaneously swing your arms from your sides to above your head. Once you have landed, return your appendages to their original positions as you jump again. Jumping jacks are advantageous because they exercise many muscles in the body, they require no equipment and you can do them for several minutes and still get a good workout