You can try to use a syringe, but without a tube small enough and the experience to know which pathway to go down, you risk squirting it down into his air sacs instead of his stomach. :/ But without getting nutrients into him, he may not have a chance. That's what saved Bean's life when she had pneumonia the other week. Are you at least able to get some antibiotics? It may not do much if it's not the right type to target whatever microbes he's got, but it's better than nothing...
I think we all need some cheering up, so I took a video of Wobbles chasing a laser pointer. I hope it can bring a smile to your faces, if nothing else. ._.