In The Goblet Of Fire Sirius is coming to Hogsmeade to stay closer to Harry. He is having a rough time there living in a cave without food and any necessities.
Sirius was wearing ragged gray robes; the same ones he had been wearing when he had left Azkaban. His black hair was longer than it had been when he had appeared in the fire, and it was untidy and matted once more. He looked very thin...
"I've been living off rats mostly. Can't steal too much food from Hogsmeade; I'd draw attention to myself."
But later we find out that Dumbledore not only knew Sirius was struggling there, he actually helped him to find the place to stay.
"You are not Sirius's only correspondent," said Dumbledore. "I have also been in contact with him ever since he left Hogwarts last year. It was I who suggested the mountainside cave as the safest place for him to stay. "
I believe from the context it's safe to assume he means the cave in Hogsmeade.
Why did he let Sirius starve and wear his old rags knowing he could't just go and get even as much as a toothbrush? Hasn't Sirius ever asked for at least food while they were in touch for months?