Thanks for the query to H.C.M. Forum.
As ,you mentioned that only vomiting
was there with blood in first vomit. Profuse sweating
are due to after effects of vomiting ,but may be also due to loss of excessive fluid ( due to vomiting) and toxins liberated by causative organisms ( food poisoning
or irritant drinks or food before vomiting).
If vomiting stop then need not to worry , plenty of fluid ( juice , salt+ sugar added water )will help.
Mind it give very less amount of fluid in a single time , frequent fluid intake will cure him after 5-6 hours.
If vomiting didn't stopped then take him in E R and get treatment .
Lemon juice with salt also helps.