Hi.
You can connect to SQL Anywhere using ADO.NET or OLE DB (and depending on the version of Powerbuilder using JDBC), but I'm not sure why you are looking for an alternative. ODBC is pretty fast for SQL Anywhere. I've been working for a long time using SQL Anywhere 8, 11, 12, 17 with really large databases and up to 50 concurrent connections without having any problem.
Andreas.