I don't know of any parser that is available externally. One option would be to download the IQ Express Edition. It is a free version of IQ, with limitations like no support, but you could use that to check the SQL. For instance, if you run the code into IQ via the dbisql utility you can specify the -n option to have it just check syntax but not run anything.
The Express Edition is available here: SAP Sybase IQ free downloads: Choose the right fit for you
Mark