One of my mother in laws dogs had pups a couple of years ago,and the mother rejected one of the babies straight away.We bought a puppy bottle at our vets which had 3 different sized teets,and hand fed her..she was fine
Its better to use a proper puppy feeding bottle because its just like their mothers teet,its alot harder for them to breath in any fluid this way because when they have finished,they just stop sucking,with a seringe the puppy has no control over the flow of the milk and this can be dangerous.Iv also seen tube feeding done (a long thin tube is forced down the throat of the puppy and in to its tummy,then with a seringe the puppy is fed without needing to suck) but I think this is for really weak puppies which cant feed on their own.I wuld go with the bottle method..you should be able to get one at a pet store or at your vets.GOOD LUCK!