It is possible to have reflux causing apneas without actual spitting up.
If the baby has had no further problems with apneas, I would suggest
getting the baby off the ranitidine.  In my limited experience, it can
cause a lot of side effects, including central nervous system symptoms
and abdominal discomfort.  Why not try just the cisapride.

Cornflour in the milk given by bottle is, unfortunately, a commonly
suggested treatment.

If this were my baby, I would spend the next 2 or 3 months in bed with
him, with the mother nursing him in bed all the time so that he gets
slow, continuous flow, and he is nursing (and thus breathing), and next
to breathing human beings.  I don't know if it would help, but parents
have done more than that for the babies.  A few months is not such a
long time.

Jack Newman, MD, FRCPC