I know it is not easy to say why which 量词 should be used when, but this one seems strange to me. Why did the author choose ‘支’?
开发出中国第一支儿童营养液,。。。
支 is normally for 'pens,guns, army divisions, songs and compositions.'
Maybe the liquid is in a bottle, which may be long and thin??
支
is the量词
of the sort of little bottle, filled with营养液
, or medicine, etc.