Diarrhoea may cause dehydration. Drink plenty of fluids to replace any lost, and use a rehydration product you may find the use of a Dioralyte preparation. You may find an increase in your salt intake (unless advised by your G.P not to do so) may help.
If you think that a certain food has affected you, leave it out of your diet for a few weeks and then try again. If you have severe diarrhoea (or persistent vomiting) – seek medical attention. If your ileostomy output is persistently watery, and you need to empty your pouch more frequently, ask your stoma care nurse for advice.