Saltines always helped me with nausea. Also candied or crystalized ginger is great for nausea.

Rice milk helps me with sour stomach, as it is so easily digested. If I eat too much oily or greasy food, the rice milk definitely helps calm things down.

Candied ginger was the only thing that helped with my nausea when I was sick from chemo. It worked FAR, FAR better than the prescription anti-nausea pills, which didn't work at all.

Anything that was a simple carb like white rice helped me.

Tart stuff like key lime greek yogurt has kick started my appetite more times than I can count. not much else seems to work for me.