Weigh yourself before and after a long ride. If you hydrated and fueled well, you might have lost 1% but not more than 2% body weight. Eventually you'll learn your needs. (you will inevitably have some glycogen depletion and the water associated with it, so, some weight loss is normal. Weight gain is a big issue though)

I've never stripped down and weight myself after a ride, nekkid and w/o rehydration and refueling. Drinking a quart of restorative is the first thing I do. However the next morning I'll be light if that was a tough ride. It'll take me a couple days to put the glycogen and water back.

I'm usually 5 or 6 pounds lighter after a hot club ride with hills and chasing faster riders for 60+ miles. I did a mountain ride and tried to conserve water early (so I could stay with the group) and by the time I got to the next water stop it was too late. Got nausea bad and had trouble drinking or eating and was 11 pounds light at the end. Worst bonk ever.
Did the same ride 2 weeks later and guzzled water early and a friend sagged the ride with cold drinks and snacks and I had a glorious time.

I wouldn't think you would given your long history of endurance stuff. There are many others who are still trying to figure it out. If someone thinks they may have a hydration issue, weighing before and after is easy to do. 11 pounds lost can be 5-8% of body weight and since a pint weighs a pound the world around, that is like 5-6 bottles short. A couple pounds is no big deal. Some of that is depleted glyogen and liver

What has worked for me is starting out any ride hydrated. I seldom eat before or during rides less than 40 miles. I eat healthy. Cramping has never been an issue. I am constantly drinking water during my ride. I also use electrolytes, and an ice cold fresh green coconut water is refreshing too.

Nothing beats chocolate milk. It has everything your body needs.

Your mileage obviously varies. Chocolate milk, for me, means a mandatory 30 minutes in air conditioning to let it settle; otherwise, I'll get digestive tract problems when I resume riding.

Chocolate milk is fine for after the ride. That said, I can eat nearly anything on a ride, within reason and depending on how much climbing is ahead. When I was younger I had more trouble if I ate too much.