Are you seriously going to throw in the towel over 1/2 cup water? You could pee all that out the next time you visit the bathroom!
Don't get this bent out of shape by mere ounces. Try to remember that a lb is 16 oz, and .2 or .3 lbs is just 3 - 4 oz!
The scale just shows weight change. It doesn't not tell you weight composition.
You go chug 2 cups of water and you will weigh more even though water is 0 calories and you know it isn't fat tissue responsible for the change on the scale. Hold some rocks and scale shows a change in weight and you KNOW it isn't fat tissue responsible for the scale.
There will be daily flux -- take it in stride and keep your perspective if you are going to be a daily weigher. I can change up to 3 lbs over the day as I eat, drink, pee, poo and I know it isn't suddenly 3 lbs of fat tissue flying around. That would be 10,500 extra calories I'd have to eat to become actual fat tissue!