"To Each Their Own" Everybody's different. Generally sticking with bland and not spicey is less likely to cause problems, but the nausea from chemotherapy doesn't have much to do with food. Much of the cause is because of central nervous system receptors which is why it is important to get appropriate anti-nausea medicines before even getting the chemotherapy- to hopefully avoid the nausea in the first place.
No set answer. This is very individual. However, foods with complex smells seem to invoke more nausea. Another trick is if your food is covered with a lid or has just been micro-waved...Have someone else open the lid and let it air lout in another room before bringing it in to you. Removing the lid and getting hit with a concentrated dose of the aroma seems to cause more nausea than anything.