SPARQL is actually two different things: Query
Trellis supports SPARQL-Update via the PATCH HTTP method.
SPARQL Query is not supported, and there are no plans to support it. That said, there are two mechanisms that may be of interest.
One option is to replicate the data stored in Trellis in an external Triple Store (which would support SPARQL Query). There is some sample code in https://github.com/trellis-ldp/camel-ldp-recipes/
that does exactly this. Another option would be to index the data in a simpler index (e.g. elastic or solr) and write a Triple Pattern Fragment
API on top of that index. The latter option will be more scalable, and there are ways to move the query execution/analysis into the client app such that a server can effectively support full SPARQL while only implementing a TPF endpoint.