As an experiment, I weighed 3-4x a day for over two weeks, just to get the low-down on the water weight. And I still do it, just to see what it is.
For instance, I am now down to 169.
This morning, I weighed 171.8 (had a LOT of sodium in my dinner last night)
and after breakfast, I was 172.6 - we're talking a matter of 45 minutes here. You literally CANNOT gain that much "weight" in that amount of time. It takes 3500 calories to equal a pound.
It's water weight, and it fluctuates all during the day, every single day. Don't sweat it!
FTR, I weigh 1st thing in the morning, after I wake up, after I pee - & I weigh completely naked (who wants to know how much their clothes weigh? I don't!) - that is the number I use as my "true weight", even tho I weigh several times a day to see what water weight is gained/lost.