No, sleeping without a bra does not increase breast size. Breast size is primarily determined by genetics, hormones, and body weight. Sleeping without a bra has no direct impact on breast size or growth.
The idea that wearing a bra during sleep can prevent sagging or promote breast growth is a common misconception. Breast sagging, also known as breast ptosis, is influenced by factors such as age, genetics, pregnancy, breastfeeding, and changes in body weight, rather than whether or not a bra is worn during sleep.