I Had The Flu For About 3 Days, The First

I had the flu for about 3 days, the first day I didn't eat anything and barely drank any water yesterday I ate only one meal in the evening, today I was able to eat more normally and now
My saliva is bubbly and I have a hard time drinking water unless I add lime or lemon juice. Is there a way to get rid of the bubbly saliva and what causes it