What is the Church's opinion on drinking holy water as a healing or meditative practice?
Generally speaking, although there may be some pious folk practices some Catholics engage in on their own, in the Latin Catholic church holy water is a sacramental intended for the purpose of engaging in blessings. Ordinarily, it should not be adapted to other, profane purposes, such as using it for drinking. If a Catholic wants healing, he should consider approaching a priest for the sacraments of confession and anointing of the sick. If he wants to meditate, he might use sacramentals designed for that purpose, such as the rosary.
Of course, if drinking holy water is an approved use for a sacramental in Eastern Catholic churches (as distinguished from an unapproved pious folk practice), then an Eastern Catholic is free to follow the approved customs of his own church.