This video, featuring three Russian women, shows an "Injection Game": giving shots to each other as a penalty for losing the game (in this case, a hand of cards). This is very similar to some scenes in the EXPERIENCES novels. For example, in BIRTHDAY EXPERIENCE, Kelly and her friends play a game of poker, and get swats or shots as their ante and bets for each round.
Needles and shots aren't (quite) as bad as they look, but can be very intimidating, psychologically. Such 'play' can be done safely, if all of the supplies are sterile, and single-use only, and if proper procedures are followed.
You may find this strange ... or it may be a turn-on, to see someone bending over and taking a shot as part of a game. As with the EXPERIENCES novels, I hope this is interesting for you, and perhaps will act to expand your fantasies.