I did this with an ex-girlfriend a few times. It was at the time a long-distance relationship, and she was visiting me for the weekend. I gave her an enema (her first ever), which she enjoyed. I gently rubbed her clit while she took the water, and while she said she enjoyed the interesting feeling, she kind of panicked when she started to feel full and asked me to stop and let her relieve herself.
When she was done and came back in the bedroom she had a big smile on her face and said “man, that really cleans you out, doesn't it!"
She next gave me an enema - my first from someone else since a few when I was very young child. Big moment in my life, and a memory I'll always cherish.
After a round or two of sex, some rest, and a meal, I asked if she would be up for a simultaneous douche and enema, and she agreed. She'd only ever douched at that point with disposables (and did so very infrequently), so she attached zero erotic association with them. But, she'd found the enema somewhat arousing and was thus intrigued by the idea of a warm, much larger douche.
I was rock hard from the moment she agreed. The go-to fantasy in my spank bank was about to come true. I know that normally when you read something like that, a horrible disappointment immediately follows, but not so this time.
We had one bag hanging from a towel bar for her enema, and another hanging from the shower head for her douche. Facing the shower head, she leaned forward while I inserted a well-lubed douche nozzle in her ass and clicked open the clamp. She stood up straight and started masturbating as I exited the tub and then reentered to face her. She quietly moaned in pleasure as I lubed the other douche nozzle and slipped it into her pussy. I guided her left hand to hold the douche nozzle in place. I stopped the enema for a minute or so to let her focus on the douche, then gently squeezed her lips around the nozzle and opened the clamp aa she continued stroking her clit. As I released her labia to let some water out, I reopened the clamp on the enema. I kept periodically closing and opening her pussy lips to retain and then release the douche water while the enema filled her. She kept masturbating with increasing urgency. Her moans were a clear indication that she was thoroughly enjoying my ministrations and was nearing orgasm. Aa the last bit of the douche water was leaving the bag, I once again closed her lips to help her hold it in with my left hand and with my right hand started slowly fucking her with the douche nozzle in her ass. That's all it took.
Her orgasm was unlike any I've witnessed before or since. It buckled her knees and she cried a bit. The water still in her pussy shot out with great force on her second orgasmic contraction. I continued to slide the nozzle in her ass gently in and out as her body continued to pulse. I know it could not have been, but it seemed like her orgasm lasted for a solid minute.
As she was catching her breath, she told me it was by far the most intense orgasm she'd ever had, and she asked me to stop the flow of the enema. I told her there was no need because she finished the bag this time. Then I gave her a kiss, removed the nozzle from her ass, and left her in privacy so she could expel. It was probably the most erotic encounter of my life.