Everybody is different, of course, but I had the same symptoms on different flights.

I am notorious for not drinking. I seldom manage more than one glass of water a day but I drink at least twenty to thirty coffees....

The cramps might be a result of drinking little but also of not moving sufficiently during the flight. No matter what the FA's tell you, walk about on long flights.

If the cramps persist, just take a magnesium tablet or two. Cramps are often the result of lack of magnesium. But this would be the case only if you were having the cramps from time to time at home, like when stretching or after a night's sleep.

Everybody's feet swell on long flights... Did I tell you my story about a flight from SYD to ATL where I was not able to get into my shoes upon landing in ATL? I had to walk all the way from the plane into the parking lot in my socks