Your body is telling you that it's hungry and/or dehydrated (thirst is often confused for thirst), and the salt craving is an indication that you need to replace lost electrolytes.

If you're counting calories, then bagging something before the ride to eat at the end of it is your best bet. I don't do it as much anymore, but I used to bring a thermos of chocolate milk to drink after rides. It was pretty good at staving off bingeing once I got home.

As a side note, I'd suggest being careful about relying on the calorie "estimates" from HRMs. They usually overstate calorie expenditure.