You could try getting someone else to give him a bottle, if you leave for a mock outing and a carer tries it may be easier, sometimes they just think why they hell would I have that when you are right here. Maybe not even a bottle, have you tried a sippy cup, try with or without the valves though, sometimes they are to hard to use. Let them play with it and become familiar to it. Is it ebm or formula, sometimes the different taste is offputting as well.

Food is for fun until one, as the saying goes. The most important part of their diet this this age is milk, so don't be concerned about the volume or regularity that he eats. Just offer healthy bits and pieces and see how he goes and always offer milk before food. Good luck!