So I bought a bottle of Benylin and some diphenhydramine caplets, as recommended by some of the users here. I figured that I since I am seriously prone to nausea I needed all the help I can get.
I start off taking a sip from the bottle, then deciding it was too gross to continue as normal, so I go and get a 2L bottle of Sprite to wash down each gulp which helped to reduce the amount of time I was exposed to that vile taste. Eventually I decided the best way to do this was to pour the desired amount of syrup into a glass measuring cup so you do not need to guess when to stop; just down it like a shot. I was also munching on some gluten-free rice crackers, as suggested by the DXM FAQ.
I drank about 75mL of Benylin, which should be around 225mg of dextromethorphan landing a person of my weight (165lbs) to the second plateau and took a 25mg caplet of Benadryl about 10 minutes afterwards once I noticed my stomach feeling funny.
The next hour was spent mostly on the computer. I told a bunch of friends via DM that "I just drank a whole bunch of cough syrup", then answered any questions they had about it. After exchanging a few messages I decide to start watching that episode of South Park where they all drink a bunch of cough syrup. About 30 minutes in now, and during the show I occasionally message a few people on my phone and this is where I start noticing my vision starting to go blurry, yet somewhat sharper as well. Colours were becoming subtly more vivid, and this effect was intensified as the sun chose this moment to set. My stomach also began to churn more and more. I go back to message some friends complaining about my stomach: "Ugh, I'm never drinking cough syrup again. I feel gross." 'Ugh' described how I felt perfectly. I was guaranteed going to puke, so I heated up my Arizer Extreme Q and filled a cannabag up with Death Bubba vapour in an attempt to keep everything down. Then I make my way to the toilet, taking my cannabag with me.
1 hour in. I sat on the toilet with my head down, unable to move, taking short but deep hits from the bag, thinking about how shitty I feel and how shit refuses to exit my butthole. I do manage to pop out a few rabbit pellets, then slowly/drunkenly head over to my bed to lie down, tossing my half-finished cannabag on the computer chair and dismissing the entire experience as a sickening mess. Wait, I do feel drunk. Not exactly, but I do feel really light and disoriented. Wait, hold on...
1 hour and 30 minutes in. As I slowly emerge from the face-down fetal position I had placed myself on my bed, I start hollering involuntarily. My vision very quickly turns into this rapid-fire film reel; it looked as if someone was flicking the light switch on my eyes on and off very quickly. My tumbly still be rumbly, but not nearly as much, it just felt really loose, like shrooms. I get more and more stimulated and eventually I manage to turn on some music and start dancing. I would probably have appeared as a drunken idiot to an observer, so it was a good thing I was alone. I did make a few videos of myself, though. It felt really nice to dance; my movements were very smooth and I felt really in tune with the music. It was a lot like dancing after drinking fair amounts of rum & coke. My eyes were wide open and my pupils were dilated to shit. I appeared to be constantly starring off into the distance and looking around like a lost puppy with tongue hanging out and everything, as well as hyperventilation at some points. The hollering continues, sounding kind of like Zoidberg as I pace quickly around my room, my bathroom, and the rest of my house freely since nobody else is home.
2 hours in. Eventually one of my roommates comes home from work and I get excited and want to share the experience with her. I open my door as she attempts to turn the key on hers, yell "HI!!" and stare at her with wide-eyes and an open mouth for what feels like 5 seconds before deciding to approach her and tell her "I'M ON HARD DRUGS". I could not stop the hollering, it was great. She goes to the kitchen to make herself some Peppermint tea and I keep her company as she explains how her day went. Since she had to go to school the next morning, we do not hang out for long so she says goodnight and I yell it back at her as I continue my robowalk around the house.
Speaking of the robowalk, I think everyone should walk like this.
3 hours in. I call up my mother to explain to her what I was feeling and we have a laugh, as I had told her I had bought some cough syrup a few days ago for the purpose of trippin' ballz, and really DXM feels manic enough to be described exactly as "TRIPPIN' BALLZ". Psychedelics seem super chill to me, although I have only really tried shrooms, and DXM is anything but chill. It is like a combination of alcohol and phencyclidine. 3 hours and 20 minutes in, I decide to go and get something to eat so I put on my coat and pants and head on outside, then realise it is 10:37pm and the grocery store is closed and the falafel place across the street that I frequent probably would not appreciate me coming in an hour before closing. Also, I was still high out of my mind and hollering so they probably would not appreciate that either. So I head back inside and opt for some crackers and hummus, and quickly realise eating on DXM is like trying to steer a car using only your mouth. I felt really uncoordinated with my chewing, and swallowing felt extremely risky since I did not have much feeling in my throat. In fact my entire body was numbed out, especially my extremities (head and hands, not sure about feet).
4 hours in. The nausea was completely gone and I was ready to relax, so I gut 'n' roll a Philly with a gram of L.A. Confidential and smoke what may have been the most pleasurable blunt of my life, laying back as I watch one of my old music video playlists on Youtube, which consisted mostly of Lil Xan, Lil Peep, Lil Skies and The Beastie Boys. About 5 hours into the trip, I decide that I am tired and ready to pass out so I went to the bathroom, took another shit and a piss, brushed my teeth, took out my contact lenses and did just that.
Overall, it was a really fun experience that was well worth the nausea during the onset. My thoughts were not really affected; I was still conscious throughout the whole experience and took mental notes on how my body was feeling. My actions/movements and vocalizations were for the most part involuntary but I was not scared so I had a lot of fun with it. My favourite part of the trip was the dancing, and of course, doing the fucking robowalk. I think everyone should walk like this.
I probably will never do it again, though.
EDIT: A few things I forgot to mention. One, this happened last night, and I woke up feeling pretty normal. No afterglow nor hangover, just fond memories of the night before. I cannot remember what I dreamt about. Two, although it felt that I was guaranteed going to vomit, I managed to keep all of it down (praise ganja). And three, I did get closed-eye visuals in the forms of emerging geometrical patterns and monstrous faces and I am pretty sure I saw some grassy fields at one point as I was lying down before and after the manic/dancing part of my trip, but this was not a significant part of the experience to me as I used to commonly experience these types of CEVs at baseline before ganja came into my life.