What Cause Fever, Vomiting And Baking Soda Smelling Stool?

hello, my 2 year old son just had a bowel movement but it is a pea green liquid and smells like baking soda. I just tried to feed him his lunch and he did not want it (which is rare because he will eat like a linebacker if you let him). And just as I was starting to type this out he vomited. He has a very low grade fever. Not sure what I should do for him. Any insight would be great. Thanks