My son is 10 months old, and i give him 100% apple juice and he chokes on it while drinking it no matter what?

i dilute the apple juice but it still seems to choke him...a lot of others juice he tend to throw back up with a lil flem/cold in it and i was wondering why...for the most part of his life he was never ever able to hold down his formula until about 7 or 8 months, doctors seem not to be worried but i want to know anybody else opinion