Sleep does not invalidate fasting, but for a fasting person to spend most of the day asleep is a kind of negligence on his part, especially since the month of Ramadan is a special time and the Muslim should strive to benefit from it by reading Quran a great deal, seeking provision and acquiring knowledge.

There is no sin on the one who drinks or eats during the day in Ramadan by mistake and his fast is still valid.

If a fasting person swallows his saliva, that does not invalidate his fast even if there is a lot of it.

Using suppositories during the day does not invalidate the fast. Similarly an enema does not invalidate the fast.