Possible donate the credits to an open source project?
I suggest contacting @williamstein [0] who has been actively seeking help to fund Sage Math Cloud [1]. See post here [2] and here [3] for reference.
I'm living on credit cards -- I have no NSF grant support anymore, and SageMathCloud is still losing a lot of money every month, and I'm unhappy about this situation. It was either completely quit working on SMC and instead teach or consult a lot, or lose tens of thousands of dollars. I am doing the latter right now. I was very caught off guard, since this is my first summer ever to not have NSF support since I got my Ph.D. in 2000, and I didn't expect to have my grant proposals all denied (which happened in June). [3]
I (author of above mentioned post) would certainly be very interested if this is possible.... Feel free to email me at wstein@sagemath.com
Edit: I don't know if google cloud credits at all transferable or what though. They likely have stringent terms of usage??