Breathwork alone can easily get you to a weird, fun place.
Oh yeah. I've heard lots of wild stuff about some of the holotropic kind of breathwork. I even did it once, but I don't really trust it. Seems potentially dangerous. Plus, I read How to Change Your Mind by Michael Pollan a while ago and he had a real scare of a near-medical-emergency from that. (To be fair, he's got heart issues, so that definitely contributed.) I remember reading that part of the book hearing the bit leading up to the holotropic breathwork and thinking "oh, god, don't do it Michael; you'll regre-... oh god he did it." Lol. He had a choice between MDMA and breathwork and because his doctor told him to avoid amphetamines because of his heart, he opted for the breathwork, and I knew that might not really be that much safer. It doesn't seem he had any long-lasting negative effects. Just a spell of irregular heartbeat or something (I don't remember more specifically than "or something"). But yeah.
All that happened the time I tried it myself was a bit of tingling and a lot of hand and face... I dunno. Cramping? Spasming? Like, my muscles seized up and I couldn't relax them. Not enough to be painful. Just enough to be weirded out. No psychedelic-y sort of effects or anything like that for me personally. I might have gotten into more of that territory had I kept going longer, but who knows. I didn't have any guide or trip sitter or whatever, so I got scared and aborted when something weird happened. I don't remember how long those effects lasted, really, but it wasn't all day or anything.