Dog has been vomiting recently, and even with less food still vomits a little yellow foamy water

There are many causes of yellow foam vomiting, including indigestion, gastroenteritis, pancreatitis, and parasite infection. With large day-night temperature swings, a dog that sleeps on the floor easily catches a chill and develops gastric upset with yellow vomit.

Keep it warm and give pet probiotics to regulate the gut. If it keeps vomiting yellow fluid, take it to a veterinary hospital to find the cause and treat accordingly.