Here is a quick 15 minute AMRAP (As Many Rounds As Possible) workout.
Perform each exercise for 25 reps.
Superman
Crunches
Oblique Crunches (both sides)
Mountain Climbers
Seated Bicycle
Mason Twists
20 Seated Bicycle
25 Oblique Crunches (Left foot on right knee)
30 Wide Leg Sit Up (Keep left arm behind head and the right arm straight in front. Come up, touch toes and repeat on the same side)
35 Mason Twists
40 Reverse Crunches
35 Mason Twists
30 Wide Leg Sit Up (Keep right arm behind head and the left arm straight in front. Come up, touch toes and repeat on same side)
25 Oblique Crunches (Right foot on left knee)
20 Seated Bicycle
40 Mason Twists (With both your upper body and legs off the floor, clasp hands together and twist back and forth, that's one rep.)
15 Thread the Needle (on right side)
30 Seated Bicycle (sit up, hips/knees at 90°, pedal forwards)
15 Side Plank with Hip Raise (on right side)
25 Fifer Scissors (lay down, alternate one leg towards ceiling, one hovering off floor)
50 Crunches (Hips/Knees at 90°)
25 Fifer Scissors (lay down, alternate one leg towards ceiling, one hovering off floor)
15 Side Plank with Hip Raise (on left side)
30 Seated Bicycle (sit up, hips/knees at 90°, pedal backwards)
15 Thread the Needle (on left side)
40 Mason Twists (With both your upper body and legs off the floor, clasp hands together and twist back and forth, that's one rep.)