Sleep standing up. Seriously, this would work.
The more helpful answer?
You are experiencing mild edema. Don’t panic. It’s common and only a a major health threat if it causes hypertension.
Our bodies naturally collect fluid between our cells. Our bodies usually regulate this by bodily movement. Obviously less of this is going on as we sleep.
The fluid is there to dilute and ultimately expel toxins, allergens and excess sodium.
The easiest way to control this effect is by lowering your salt intake. There is a very direct connection between bloating and sodium levels.
Get an allergy test. Many people have mild food allergies and don’t even know it.
Drink more water and take up an exercise that sweats it out. This helps flush your body of the offenders I mentioned above.