Simplify the following text for a Grade 7 native English-speaking person.
Original: Water in cakes serves to make the base ( in the case of cakes called `` batter '' ) as thin as possible , which allows the bubbles â `` responsible for a cake 's fluffiness â `` to form better .
Simplified: Water in cakes makes the base ( in the case of cakes called `` batter '' ) as thin as possible , which allows the bubbles to form better .