Yes Coca Cola is good for settling an upset stomach and it's believed it's because of the fizz contained in the Coca Cola that helps with the upset stomach.
Other fizzy drinks such as Ginger ale or any other clear sodas including club soda and even seltzer water can help relieve an upset stomach.
Soaking in a warm bath and even drinking some water can help with an upset stomach.
Also if you feel like you can or need to throw up then try throwing up as getting rid of what's in your stomach can help clear up an upset stomach.
Sometimes I have to force myself to vomit by gagging until I vomit or sticking my finger down my throat and once I made myself throw up my stomach feels much better.