What should I eat the next few days after gastric Botox injection?

Botox is used for certain gastroesophageal problems including gastroparesis, achalasia or reflux. Nothing specific is required after the injection of Botox other than the standard recommendations for your specific problem (e.g.. keep head of your bed elevated if you suffer from reflux, small volume and easily digestible food for gastroparesis, etc.). Although Botox can be very helpful in some conditions, some other measures are often needed to alleviate your specific problem. I am sure your gastroenterologist has explained everything related to your condition; she/he would be much better resource of information on the subject than you can find on this forum. Good luck!