Every gram of carbs makes you retain 3 or 4 grams of water. When you fast your body processes (burns) the carbs and you excrete the water. You obviously get that already.
When you refeed with carbs, you regain the water again quickly (overnight). But… if you refeed keto (low carb, high fat, moderate protein) you don’t regain the water. You still refill your digestive tract and go up a few pounds carrying around that in-process food
Same process applies when you start a ketogenic diet. You “lose” several pounds initially that is mostly water weight and when you go back to non-keto those pounds come back.
Point is, the answer to your question is that it depends on how you refeed.
Side note, pro fighters go low carb before the weigh in to meet their goal and can drop 10+ lbs in 48 hours. What you can shed in retained water depends on how big you are and how you were eating before you decided to drop the retained water.
Fun fact, a gallon of water weighs 8 lbs.