This is called "Triple Threat Tee".
It's the same company that produced the 'around the world' tee seen above, and it's made for Sonic Mania. It has 3 columns of color that fade from screen-tone dots to solid. At the top of each is a sihlouette character face for the corresponding color. There's Tails for yellow, Sonic for blue & Knuckles for Red. At the bottom right is a small rectangle that spells out Sonic the Hedgehog, but in white Japanese letters. There doesn't appear to be any English at all on the shirt save for the copyright. What company is making these? It is also impossible to tell if it's meant to be classic or modern since the faces are just sihlouettes. This is a fall 2016 release.
This tee is called "The Real Super".
It...kind of doesn't make sense as a title or even half a sentance. However, it does have Sonic, Tails & Knuckles with a Green Hill CG type background. And it is a 2016 item...making it one of the first few "post Boom" modern Sonic items. (Boom would not allow modern art characters to be featured on anything for over a year by removing the license from companies) Notice the little white rectangle tag. It's the same as the above 2 "Mania" promoting shirts & also has "Sonic the Hedgehog" stamped/written out in Japanese letters at the bottom like the shirt directly above also does. It uses slightly less common art for them too, with jump/twist Sonic, away/fist Knuckles & flying Tails. Not a bad tee at all, but where can you find it?
In 2016, a company called "Tee Turtle" that only operates via online sales got a Sonic license to make a limited series of tees. (After the so called "boom embargo" lifted) They chose to do this "Sonic Cuties" series of 3 adults sizes shirts. (sold separatly) Each one has a 'chibi-type' cute little character & a slogan at the bottom.
Little Sonic looks annoyed while tapping his foot with "I'm Waiting..." (If the tee line is modern....which it is...why is the Sonic classic?) Shadow strolling with his eyes shut (actually, he's shutting his pupils...his eye lid is open) while holding his guns with "Haters gonna hate" & Knuckles lifting hand-weights while frowning with "Getting Swole".
It's a quite curious set of designs where Shadow is the most cheerful character of them all! The shirts are all from www.teeturtlle.com