SynCommerce allows you to easily filter your products by SKUs, tags, materials, and collections. To achieve this;
STEP 1: You simply have to go to the products page, then click on the "Advanced search" button by the search field.
STEP 2: In the advanced filter modal that pops up, provide the values you want to filter by. The search relationship for the advanced filter options is an "and" relationship. Thus, if you provide the value "shirt" for the tags field, and value "SHIRTKSKU" for the sku field, then you are asking to filter your products by those which have the "SHIRTSKU" sku and tag "shirt".
Click the "Search" button to filter once you are done.
Contact support at email@example.com for any further help.