Yes you can query datastream with Elastic SQL
First command queries multiple data streams, the second queries a specific data stream. I just tested this on 8.16.1
POST /_sql?format=txt
{
"query": """SELECT * FROM "logs-*" LIMIT 10"""
}
POST /_sql?format=txt
{
"query": """SELECT * FROM "logs-kubernetes.container_logs-default" LIMIT 10"""
}