hello,thanks for trusting health care magic
seen your history but would be better if i know complete details...
fainting with sweating can be caused due to many reasons like hypertension
,diabetes,low sugar levels,salt depletion in the body,hypotension,thyroid disorders,etc..but in your case looks more of like electrolyte depletion due to excessive sweating
avoid dehydration,take healthy diet with enough calories and salts,avoid long working hours in sun..
,consult a doctor and try to know the reason forexcessive sweating and causes of fainting and get well soon..