Since there is very little information about Sulpiride's interactions with recreational drugs on the internet (I couldn't really find any reports when I looked), my cat asked me to help it share his experience with Sulpiride and recreational drugs (he can't type on his own). In fact I signed up especially to help him share this information. Obviously don't take this as hard facts, as it's only anecdotal evidence from a single individual.
Sulpiride and
marijuana: no noticable difference in the effects of either drug
Sulpiride and
psychedelics (LSD and DMT): unlike other antipsychotics, Sulpiride doesn't affect serotonin receptors. This led my cat to believe that it would probably not have the same effect on psychedelic drugs as SSRIs or other antipsychotics do. My cat can confirm this to be true. It is possible to trip just as hard while on Sulpiride.
Sulpiride and
MDMA: untested, but probably works for the same reason as psychedelics.
Sulpiride and
DXM: works. Unfortunately my cat can't comment on any difference in effects to taking just DXM as he hasn't taken DXM without Sulpiride.
Sulpiride and
Salvia: works. Same as above applies.
Sulpiride and
2C-E: works. Also not tested without sulpiride so no information on difference in potency/effects.
Sulpiride and
alcohol: appears to slightly increase the effects of the alcohol but it appears to be neglible.
You can find some trip reports including Sulpiride here:
http://meatslog.tumblr.com/search/sulpiride (Please let me know if it's against the rules to link to my cat's 'blog')
Hope this helps someone. Sulpiride might be a good choice for people who want/need to treat their depression using meds, but don't want to sacrifice recreational drugs to do so.
Off topic: My cat originally was interested in taking Sulpiride for his depression because it seemed likely that it wouldn't affect psychedelics and ended up discovering that it worked significantly better than any other of the many SSRIs and antipsychotics he had taken over the years. The effects became noticeable within just 2-3 days instead of weeks and for my cat it does a much better job of reducing the symptoms of the depression. My cat doesn't understand why it's so rarely prescribed for depression. For him it was a godsend!