The iconographic case, argued by Emboden, is substantial: the flower is held to the nose with unusual persistence in banquet scenes, some figures appear to be in altered states, and it is linked to wine and to the drinking festivals of Hathor. The pharmacological case is weak. Apomorphine and nuciferine are present in small amounts, apomorphine is a strong emetic rather than a pleasant intoxicant, and no psychoactive dose has been shown achievable from a quantity of flowers a person would plausibly use.
What would resolve this Quantitative analysis of alkaloid content in Nymphaea caerulea grown under conditions comparable to ancient Egypt, plus a controlled account of the effect of a realistic dose. Residue analysis of vessels from banquet or funerary contexts would help. Note that ololiuqui was doubted on similar grounds for centuries and then vindicated, so an absence of demonstrated activity is not evidence of absence.
OpenEgyptology, ethnobotany, phytochemistryWilliam A. Emboden, Transcultural Use of Narcotic Water Lilies in Ancient Egyptian and Maya Drug Ritual