A simple Sonic 3D Blast promo shirt with a bit of a story to it. The shirt itself isn't very unusual, all games of the era seemed to have some kind of promotional tee or pre-order bonus type thing and 3D Blast was a big enough deal to not be an exception. It has the sort-of-3D looking running Sonic graphic for its design, with the logo at the top. The words behind him are the consoles it released on. In this case, it's the back of the tee with the big design, and the front has the logo smaller on one side of the upper chest area. 

The thing to note though, is the tag which is the inset item in the middle. It says "Screen Stars", which is the logo of the tee maker company. This is not unusual, but what IS unusual is the era the shirt was made in vs. the ScreenStars logo (Logos change over time sometimes, the font used indicates when it was made) Obviously the shirt couldn't be made before 3D Blast existed--but the game only came out almost 'too long' after ScreenStars abandoned that logo style.
Screen Stars refers to 2 things at once which are screen-printing tees and also 'stars of the screen' which refers to TV/Video game icons & etc so it's a clever enough name for a blank tee maker. They sold blank shirts to companies to be printed on. If you know any details about the dates of the tee, you can write in for credit & the description will be altered.