Burlap Hanging Sack
From the Super Mario Wiki
Burlap Hanging Sacks, also simply called bags, are uncommon objects appearing in several Donkey Kong games. As their name suggests, they are large cloth bags hung with a rope from an unseen ceiling.
In Donkey Kong Country Returns and Donkey Kong Country Returns 3D, each Burlap Hanging Sack is patterned with bull's-eyes and contains a valuable collectable, such as a Puzzle Piece. The Kongs can toss a projectile, such as a barrel, into the hanging object to break it, unveiling the item inside. Exceptionally, a Burlap Hanging Sack found in Stormy Shore triggers the appearance of a treasure chest upon getting destroyed, though the bag itself does not contain anything.
The appearance of Burlap Hanging Sacks has been slightly renewed in Donkey Kong Country: Tropical Freeze, displaying Snowmad insignias instead of bull's-eyes. However, they fulfill the same role as in the previous games.