one thing that i have more recently started thinking about is coughing before/while throwing up and ik it is not the most popular but here me out:
person has been involuntarily letting out nauseously coughs intermittently all day, and their friend thinks they just have a cold or something, but surprise! they are about to puke everywhere
the way a cough turns guttural and choked and then cuts off as vomit comes up
person with pneumonia/a chest illness has been having frequent and long coughing jags, and also has a lot of mucus and crap in their stomach from their illness. the repeated coughing and already unstable stomach is not a good combination
a cough morphing into a belch morphing into a wave of sick
when a person chokes on the force of their vomiting and triggers a coughing fit, but is still also vomiting and is struggling to catch their breath
coughs getting deeper and longer and more painful the closer someone gets to throwing up
a person who is both coughing and belching while vomiting, and the contrast of dryer and wetter sounds as they get sick