See if Buttons will eat out of your raised hand. Any creature that is nauseous will not want to lower its head. Check for dehydration. Grab a pinch of scruff on the back of the neck. Let go. If the skin goes down rather quickly, your cat is hydrated. If the skin take for than a second or two, your cat needs fluids. You can also check the gums. They should be moist and not tacky.