Why make it complicated? Crunches is an excellent go-to exercise and if you want to spice them up you can make them twisted.
Lay on your back in bed and elevate your legs. Raise your upper body and turn to the left and meet your left knee with your elbow or hand. Keep you legs elevate and switch sides. Do as many as you can manage.
There’s no need to raise your upper body all that much. If you just get your shoulder off the sheets then that’s enough.