nausea in dogs

What can I do for my dog when she vomits. Occasionally she gets lethargic and won't eat all day and the following day will vomit yellow foamy liquid. What foods can I offer her to settle her stomach.
   
Thanks for the advice.

once a dog vomits you must take food and water away for 2-4hours. you can give a little water back sooner than 4. Dogs don't have the ability to hold back the gag reflex once they have vomited so if you give them something to eat or drink they will just vomit it back up anyway. You might think of changing the dogs food if your dog vomits all the time or obviously a health problem. Does he/che get into the trash or eat things outside? What food are you feeding now and what breed do you have? little more info please.

She's a 9 lb. toy poodle. She eats Science Diet adult small bites. It's the only kind she will eat because I've tried several. When I introduce a new food I mix it with the SD for a few days as I have been told and she actually will sort it out. She is never outside without a leash or unaccompanied so she is not eating anything foreign. Thanks for your advice.