What is the max network latency between synchronous-commit AlwaysOn Availability Groups Is there a maximum supported network latency (ms) between two synchronous AlwaysOn replica?
I need to give this information to network administrators for configuring the link between the two nodes of the cluster.
I know that syncronization between replicas is influenced by disk speed and other things: The picture in this article explain the process involved.
The AlwaysOn instance will host the sap database (1 TB of data) and I estimate that the workload will be considerable with large transactions.
There is no maximum for the supported latency for synchronous replicas.  You will sometimes opt for a higher-latency deployment in return for a RPO=0 for a broader range of failures.  

The most common mission-critical configuration is to have a pair of synchronous replicas on separate racks in the same datacenter, and a third, asynchronous replica in a separate datacenter.  

But guidance for your scenario should probably come from SAP, or from the Microsoft/SAP Engineering Alliance.  See eg https://techcommunity.microsoft.com/t5/running-sap-applications-on-the/bg-p/SAPApplications/label-name/AlwaysOn