1
general::
Pay another's expenses, treat, as in I'll spring for the dinner this time. [Slang; c. 1900]
American Heritage Idioms
2
general::
Phrase(s): spring for something [and] bounce for something
Sl. to treat someone by buying something. • I’m bouncing for pizza. Any takers? • Ralph sprang for drinks, and we all had a great time.
McGrawhill's American Idioms And Phrasal Verbs