#!/bin/bash

Value4Variable=Value4

curl -s -X POST -H "Content-Type: application/json" -H "Accept: application/json" -d
'{"Variable1":"Value1",
"Variable2":"Value2's",  # escape of quote doesnt work because of the previous single quote and backslash
"Variable3":"Value3",
"Variable4":"'"$Value4Variable"'",
"Variable5":"Value5"
}'
https://www.hashemian.com/tools/form-post-tester.php