Your body can store sugar, fat, and water, but it has no way to deal
with alcohol other than to filter it out. When
alcohol gets into your bloodstream, your body essentially treats it like poison and prioritizes processing it.
Your body works to process alcohol first so that other things like the water and sugar may go to storage, causing water retention. Fluids start to collect in your body tissue, and gravity makes water collect in your feet and sometimes your hands.