Weight Training
Wrist Rollers
Take a wooden stick or bar, attach a rope to the middle, and tie a weight on the other end. Roll the weight up and down, rolling in each direction. To increase the challenge, try making the handles thicker and vary the grip at different angles. Grade your effort by both the number of times you completely roll and unroll the weight, and the pace at which you can roll the weight.
This piece of equipment can really blowtorch the lower arms. If you are finding it hard work on the shoulder muscles try resting the stick or bar on a metal frame or something equivalent and resume rolling and unrolling the weight. These can be bought on Amazon if making one is too much hassle. Buy From Amazon US

Lever lifts
Take a reasonably long heavy object like a log or baseball bat, and hold it in front of you. Now, lever it up and down. The further away the weight is from your hand, the harder the lift will be. For an alternate workout try the rear lift, holding the piece of equipment halfway. When you get used to the movement, go heavier. Your wrists will be in a delicate position doing this exercise, use a lighter weight!

One Sided Dumbbell
Another simple method for training the wrist without unusual equipment is to simply load one end of a dumbbell and perform exercises like rotating the hand right, left, up and down while not moving the elbow.
You may want to support your forearm across your leg or a bench while doing these in a seated position. A towel or thick cloth can be wrapped round the unweighted end of the dumbbell to prevent the thread digging into the hands.
Plate Squeeze
Grab a pair of Olympic plates placed side by side with the smoother sides on the outer edge. Rub some climbers chalk on the working hand and inside the plates to counteract any moisture. Squeeze and lift for as long as possible. This exercise should be performed over a soft surface should you happen to drop the plates at any point.

You can also try lifting a plate by the center hub, by grasping it with just your fingertips and thumb. Again white chalk will help here.

Bucket Belt And Pliers
Find a Bucket, a pair of pliers and an old leather belt. Fill the bucket with gravel, sand or water or anything else you may have. Place the leather belt under and around the handle of the bucket and grip with a pair of pliers. The heavier the weight, the more force you'll have to exert.

Plate Curls
Grab some disc weights between the fingers and thumb and grab with a pinch grip. Rest the back of the wrist over something strong and curl the plate upwards towards the ceiling. Alternatively try curling the plate with the front of the wrist down. You will be surprised how hard this exercise really is.

