What they mention in the API docs is that you can create a job with sql_task of type Alert. To make it easier you can try creating the job first in the UI first and downloading the JSON config. Here is an example with the main parameters that should work for what you are trying to do:
{
"job_id": 1111,
...
"settings": {
"name": "test_sql_task",
...
"schedule": {
"quartz_cron_expression": "34 30 20 * * ?",
"timezone_id": "UTC",
"pause_status": "UNPAUSED"
},
"tasks": [
{
"task_key": "test_sql_task",
"run_if": "ALL_SUCCESS",
"sql_task": {
"alert": {
"alert_id": "009f4ff1-0493-4e58-9224-7ea4dcca0f99",
"subscriptions": [
{
"user_name": "test@email.com"
}
]
},
"warehouse_id": "475b94ddc7cd5211"
}
}
],
...
}
}