Here is a full page ad with a collaberation promotion of Moo Town Snacks & Sonic 3D Blast. This likely appeared in game magazines or comic books at the time of the game's release. Mootown snacks are cracker packs of various types meant for lunch boxes or snacking. They featured items like cracker or pretzel sticks & "cheese flavored product". This had nothing at all to do with actual dairy, was non-refrigerated and merely cheese flavored. That's where the whole cow connection comes from, though their cow mascot was male/a bull. On the packages you could collect "point panels" (cut off part of the package) called "Cow Chips" & mail in / redeem them for merchandise or enter contests with them. This ad explains all that and shows you...

The cross-promotional goods you could get. You needed A LOT of points to do anything. Like a family eating the snacks every week, to get points before the promo expired. You can see yellow headphones with Sonic logo, a previously released watch on a card, Archie Sonic Comics, a MooTown hat (nothing to do with Sonic) and a really unique tee. The tee featured Sonic & the Mootown mascot in "3D" with glasses so you could look at your shirt. The tee itself is rare, though not that desireable as it is strange.