GCP VMs are per-minute, with a minimum of 10 minutes (vs AWS' new minimum of 1 minute). Second resolution is nice, but I doubt it makes much difference in pricing for most workloads. https://cloud.google.com/compute/pricing#billingmodel
Azure's containers don't use a full VM-- they're more like AWS Lambda or other serverless frameworks, so they do per-second billing with no minimums.
Disclaimer: I work at Google on Container Engine.