Feral cat acting sick at night...

My mother started taking care of a feral cat during a winter storm back in February. Since then she had him neutered. 

Last Wednesday he started acting very lethargic. She brought him inside, gave him water with a needle-less syringe, gave him some tuna juice, and babied him all night. The next day he was better. Running around, eating, and even fought with her to get outside. (She's keeping him inside to keep an eye on him) Last night around 4:30 in the morning he was meowing loudly. He was laying on the floor with labored breathing, he wouldn't move, and he couldn't hold himself up. He honestly looked like he was in the process of dying.  She stayed up with him all night giving him water from a syringe. Around 7am... He was fine. He's not as active as he normally was. She's been giving him water, wet cat food, tuna, and an antibiotic our neighbor gave her. She can't afford to take him to the vet due to her limited income. I've contacted a local feral cat organization in hopes to help, but doubt I'll hear from them until Monday. I was just wondering if anyone has any idea of what could be going on. 

Thank you for the help. I did try yahoo answers, but they were quite rude.

I would not be giving the cat a human antibiotic from a neighbor.  That could do more harm than good.  The cat needs to be seen by a vet.  I would call around and see if you can do a payment plan or find a low cost vet in your area.  It may take a long time to hear from rescue groups this time of the year as they are swamped.   Reach out to friends to see if your Mom could borrow some money.  Continue to offer fluids.  You can try Gerber stage 2 baby food in chicken or turkey.  It's in a small jar with a blue label.  The only ingredients are turkey/chicken and water. 

Keep him inside and comfortable. 

I am sorry about the feral cat.  Do your best to find a way to get him a vet.

If he is allowing your mom to care for him, he is not completely feral.  He may be a stray who's gotten used to living on his own but he seems to understand your mom is helping.

Unfortunately, he does need to be seen by a vet.   It sounds like he has a disease or infection that is causing his issues and the vet will be able to identify which one.  Not every antibitic works on all infections, so you may be giving him the wrong one.

Fingers crossed that rescue agencies can help you.  They are usually swamped this time of year, as ShadowsRescue said.

Give your mom my thanks for helping him - not everyone would have done so.

He's doing MUCH better. The antibiotics from my neighbor were for her cat.  

He had an infestation of hookworms. The vet gave us a medicine, and said he should be fine! Thank you for your help.