hand to mouth, from
With only the bare essentials, existing precariously. For example, After she lost her job she was living from hand to mouth. This expression alludes to eating immediately whatever is at hand. [c. 1500]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.