itch.io

I haven't achieved it either, I don't have the patience to play and check but it's called "hollow bride" in the image files and "liquid" in the code. The code for it is different from the Parasite and Anomaly paths but I haven't been able to reverse-engineer either, it's a bit of object-oriented mess. However, upon closer inspection it looks like healthy liquids might not actually increase the liquid level, see last line:

for keys in [Content.UNHEALTHY, Content.PARASITE, Content.ANOREXIA]:
    if health_lvls[keys] > 0 and val_count <= 3:
        health_lvls[keys] -= 1
    else:
        val_count += 1
        if val_count == 3:
            health_lvls[each] += 1
            if count.has(Content.LIQUID):
                if count[Content.LIQUID] > 0:
                    pass
            else:
                if count.has(Content.HEALTHY):
                    if count[Content.HEALTHY] > 0:
                        health_lvls[Content.LIQUID] -= 1

Anyway, ¥100 is best for anomalous liquids too (11 %: bottled blood/eyes/sewage) and ¥150 for unhealthy liquids (100 %: Kola Classic/Zero/Chost). So maybe anomalous and unhealthy liquids are a way to go?