Apple's cash generated by investing activities 2015-2024

Proceeds from maturities of marketable securities generated the most cash for Apple in its 2024 financial year. The company generated over 50 billion U.S. dollars from this investing activity. 
Maturity, or maturity date refers to the final payment date of a loan to other financial instrument. Marketable securities are debts that are to be sold or redeemed within a year.