You can configure the offline database to accept case-insensitive values for string comparisons.
By default, the offline database is case-sensitive. For example, when executing a case-sensitive comparison operation, an upper-case letter "S" and a lower-case letter "s" are treated as unique values returning no match. When case-insensitivity is enabled, "S" and "s" are treated as equal values returning a match.
case_sensitive_offline_db=no
http://services.odata.org/V2/OData/OData.svc/Products?$format=json&$filter=substringof(tolower(Name) eq 'bread')
http://services.odata.org/V2/OData/OData.svc/Products?$format=json&$filter=Name eq 'bread'