This hat is called "Hedgehog in Training".
It is a camo patterened military / army stale cap hat. It has army-green printing on the front in a 'stencil' type font with the slogan. Because the hat is similarly colored, the slogan is blending in. The cap has wear/weathering on the brim. This is a Sega Shop online item in 2018, and is $25 dollars.
Clearly, another Sonic Forces item, because everything for that game is set up to be grunge/military. Certainly, it's unique among Sonic stuff for...not really having much to do with Sonic? Maybe it's trying to be subtle but it comes across as a tad plain with a not so sensible slogan for something as costly as 25 dollars.