A black tee with the slogan "A Whole New Speed of Hero". This has the movie's logo & a circle with pointing movie Sonic in it. Of course, he's CG like in the movie, and also poorly lit on purpose.
Why he's shadowy is anybody's guess, but that's a common theme in the clothing, shading him out to hide the details of the moviegremlin design. The movie didn't take place mostly in the dark so...
This is a SegaShop item, and it is unfortunately about 30 dollars in adult sizes so that's kind of expensive.

Here is a long sleeve black tee for the movie.
It's called "Movie Hero Tee". It uses the 'very shaded/shadowy' CG of Movie Sonic in a bit of an awkward pose in front of the orange/purple fade background that is used on several other items. It has the movie logo at the bottom & the "Whole new speed of hero" slogan is in that blue bar you see that is small, under the logo.
This is a Sega Shop exclusive item, and is 30 dollars in adults sizes.

Here's a long sleeve medium blue tee.
This time, the Whole New Speed of Hero slogan is on one sleeve, written vertically. It has a really big logo for the upper chest area, and CG movie-Sonic holding a ring is the design. There are more of the trapezoid color theme, this time for the background. This is set up to make him look a bit 3D by having him overlap out of the largest shape.
This is a SegaShop item and it is about 40 dollars, because it is a long sleeve.

An item that's...probably not worth its while.
This is a plain black hoodie type sweat shirt with draw string hood. It has the movie logo large across the chest area, and that's it. No other decorations. So, it's basically just a plain item with 0 design effort into it and it's somehow 70 dollars in the SegaShop. Unless this thing launders itself....that's a lot to pay for having some logo stamped onto a generic thing like this is.

Kohls department stores gets a movie item: and it's this gray tee.
Their stuff tends to be exclusive to them, but you can buy this online at their website as well as in the store itself. It's a plain gray tee with running (as usual) movie CG Sonic fairly large on the bottom left. The design looks like it wraps around to the back of the shirt. The movie logo is added above his foot. You can see there's likely a printed in collar tag as well.
This is a summer 2020 item, but in July you can see that it is already on markdown. (Was Movie stuff just not that popular as merch?) Did anyone even know Kohls had this? Sizes for 8 to 20 means it'd likely fit anyone.

Annnd maybe another item that is likely not worth its while either.
This is a gray sweat shirt with 'kangaroo type' single front pocket. It has draw strings for the hood, but no zipper. It's also completely plain and ordinary, except for a small logo from the movie on the left side of the upper chest area.
And it's 40 dollars.
This is another of the Sega Shop's 'barely any effort' items. How is this Sonic? Who is such a huge fan of the movie that they want a teeny tiny logo on an expensive and otherwise plain item? It's just too generic to be worth the 40, even if it is large/adults sizes or anything.

Here's a black tee with 'baby version movie Sonic'.
It uses the movie logo large at the top and places CG baby version a bit in front of it. Here, he's holding out the Green Hill-specific geometric type sunflower but it's very small as opposed to how it is in the game. He has shoes on with this version, although the legs are barely visible. This is clearly trying to play to 'oh we made him cute now' , to appeal to anyone who really likes baby-version. It's a Segashop exclusive in adult sizes and is 25 dollars.

These tees are nearly variants of each other. The first is dark blue, the second a dark charcoal. They've got the same running/triangle Movie Sonic with the same logo too, but the lighting used for the art is different. The dark blue has normal lighting, and the charcoal has it with the deep shadowing/darkness effect applied to shadow out most of his body/legs. The triangle there is also filled in with a bit of gradient color. These are Segashop items.