cramp at night

You stretch your ankle muscles by bending and flexing your foot from the ankle.

Try drinking two large glasses of lightly salted water in the course of the day. Unless of course you have medical problems that make it unwise for you to consume extra salt.

Muscle cramps can be caused by dehydration or by lack of salt, so drinking salted water should help.

Any gentle exercise you can take in the course of the day, such as walking instead of going by car to the nearest shops will tend to strengthen your leg muscles which may make cramp less of a problem.

I too suffer with ankle and toe cramps at night. I find if I twist my foot on it's side and hold it for a count of 30 or so and then twist the other way and hold it does eventually go. Toes I stand on tip toe whilst leaning against the wall.
Drinking tonic water us supposed to prevent cramp.

Magnesium helps with cramps.

If you're somewhere hot at the moment, yes, you may need more salt if you're drinking lots of water, but if you can find magnesium tablets or powder, I would recommend taking some before bedtime.