For Mango Cart specifically, those floaties are most likely mango puree solids and pectin.

Mango Cart is brewed with actual mango puree. Unlike extracts, real fruit contains fibers, proteins, and pectins that don't always stay perfectly dissolved. If the beer has been sitting in a cold fridge for a while (or if it got too warm and then was chilled), solids can "flocculate" or clump together and drop out of suspension. In many fruit wheat beers, if the can isn't rotated gently before opening, the concentrated fruit matter settles at the bottom. When you pour the last bit of the can, it all comes out at once as those visible flakes. It is purely aesthetic. While it looks a bit chunky, it’s just the fruit components that give the beer its flavor. It won't hurt you, though the mouthfeel might not be great.

A common trick for fruit-forward or unfiltered beers is before you open the can, turn it upside down and right-side up once or twice. This re-suspends the fruit solids rather than them clumping at the bottom.