I once tried it and got a second more agonising cramp

Boof magnesium

Standing up works every time for me. If I want to remain in bed i try to push the bottom of my foot into the bed as if I were standing on it. It often does the job .

This trick has become a reflex for me, to the point where I barely even wake up when I get a Charlie horse in the middle of the night, since I start flexing my foot automatically when I feel it coming on.

Similar trick I learned, just get out of bed and stand up on it. It'll go away in ~10 seconds and then you can hop back into bed. Works pretty much every time.

This is how you fix a cramp scuba diving - grab the tips of your fins and pull up. Same effect. Works for me too.

Alternatively, start eating properly and solve the problem at its root.

Foam rolling + active release works better than pure stretching IMO. Also be sure to get your micronutrients in.

Edit: I should clarify this is intended for maintenance, not in the moment relief of the cramp.