I wouldn't call it a strait jacket. That would be when their arms are like...wrapped around themselves. Maybe its like a special gimp suit with their wrists tied to their upper arms and such?
It’s a piñata, and Blossom is being forced inside it with a bunch of candy and condoms. She’s wearing a bitchsuit/human dog suit to force her limbs to contour to the dimensions of the stubbier arms and legs of the piñata’s. The “recipe” Bubbles is holding is likely instructions from whoever wanted her in the piñata telling them what to do as Buttercup shoves Blossom in with the goodies, or more likely what Blossom wants done to herself. Blossom doesn’t seem to be resisting so she likely is consenting to whatever is happening, and will be used as a sex doll if the mouth opening is any indication of what’s to come. The bitchsuit along with the candy and condoms could indicate some rough play/CNC BDSM scenes would follow being released from the suit. Blossom’s partner may also opt to continue to follow Bubbles’ “recipe” if it was actually a script by Blossom herself and made to be left as a sort of set of directions on what she wanted done. This would allow clear communication without having to worry about misunderstandings over safe words when words aren’t able to be used due to gags being in play. Blossom, having been secured in her piñata, would only have to lay back and wait for her partner to arrive to start the scene.