What is the best treatment for nausea in a cancer patient?

Medications. There are many medications that help with nausea and work in different ways. For chemotherapy-associated nausea some of the best medications are the 5ht3 antagonists such as ondansetron. Other types of nausea medications can be used alone or in combination with the 5ht3 drugs for optimal nausea control.
Nausea and CA. There are lots of different medications to use for nausea; ativan, phenergan, (promethazine) compazine, zofran...The list goes on. Some are you take by mouth others are iv. And if all that fails you can always try things like sweet potatoes and blackberry wine :).
No best. There are many drugs that help with chemotherapy induced nausea; zofran, compazine, (prochlorperazine) emend, dexamethasone, Ativan to name a few. Some drugs are better for certain chemotherapies and some drugs are better for certain patients.