Imitate available variables:
{% set my_test_json = {
  "temperature": 25,
  "unit": "°C"
} %}

The temperature is {{ my_test_json.temperature }} {{ my_test_json.unit }}.

{% if is_state("device_tracker.paulus", "home") and
      is_state("device_tracker.anne_therese", "home") -%}
  You are both home, you silly
{%- else -%}
  Anne Therese is at {{ states("device_tracker.anne_therese") }}
  Paulus is at {{ states("device_tracker.paulus") }}
{%- endif %}

For loop example:
{% for state in states.sensor -%}
  {%- if loop.first %}The {% elif loop.last %} and the {% else %}, the {% endif -%}
  {{ state.name | lower }} is {{state.state_with_unit}}
{%- endfor %}.

{{ now() }}