What kind of antacid can I give to a month old kitten for a stomach upset

My 2 year old female cat has been vomiting for a couple of days now. She was spayed a few months ago and I feed her dry cat food. She is active and normal otherwise. She is well hydrated and drinks enough water. But the vomit is concerning me. The vomit is digested food. And twice it was undigested food. The only vet in my town is unavailable at the moment and I am really worried about my cat. What should I do?

Cat started vomitting a week ago when we were out of town, mostly food and hairballs. Took him to the vet when it became bile. Vet did a nausea shot, blood test, and xray. All of these came back normal. Vomitting bile and not eating started happening again 2 days later so I took him back in they gave him a anti nausea shot and a antibiotic for infection possibility. Two days later we are back to vomitting food and water. The vet mentioned scoping him if this did not work. I am curious what is all causing this and are we taking the right steps?

Kuro is less than a year old, and an indoor-outdoor cat. She has no previous health problems and was fixed and vaccinated as a kitten. She is a short hair, but our house is generally hairy because the elder cat, Izzy, has very long hair. During Christmas my boyfriend and I both left and couldn't take her or Izzy, so we left out 3 days-worth of food and took out the trash. When we got home there was both food and water left, and Kuro appeared to have suddenly gotten fat. We assumed she just overate. We also noticed the bathroom trash can was knocked over, but there was just tissues and q-tips, so no chance of spoiled food. Then two days ago she vomited food mush and white mucus and was tired after, and tonight vomited again, this time with food mush, white mucus, and a small amount of clear liquid with white foam. Her energy afterward is fine. I have been home most of the time the past two weeks, and have not observed any behavioral, eating, or drinking changes, and when I cleaned the litter today everything looked healthy. Her abdomen doesn't seem sensitive when we apply pressure. But I am concerned about the sudden apparent weight gain and vomiting. Could they be related? Thanks for your input.

A week ago our short haired oriental boy, who is 7, had his annual booster vaccination. By the evening of that day he was clearly unwell, as in very lethargic and not wanting to eat. He also felt really hot. He continued to go down hill, vomited bile a few times and was drooling. Back to the vet who kept him in and put him on a drip because by now he was dehydrated. This is the third day he has been with them and we just had a phone call to say he has produced a huge amount of vile, blood stained diarrhoea, but we can bring him home should we wish. I have suggested to the vet that he’s with them for another night and they will let us know in the morning how he is. He still hasn’t eaten anything. Getting really worried now.