1 Corinthians 10:18-20 provides vital instruction that every believer must heed:
1 Corinthians 10:18 Behold Israel after the flesh: are not they which eat of the sacrifices partakers of the altar? 19 What say I then? that the idol is any thing, or that which is offered in sacrifice to idols is any thing? 20 But I say, that the things which the Gentiles sacrifice, they sacrifice to devils, and not to God: and I would not that ye should have fellowship with devils.
To eat in a worship context of what has been sacrificed on an altar to an idol is to be a partaker of the altar. To do so is also to have fellowship with demons!
Such fellowship with demons is not contingent upon a person's having to offer the sacrifices himself. Anyone who eats of such sacrifices comes into fellowship with demons.
The passage also does not provide any basis to say or to hold that this only happens sometimes--in a worship context, anyone who eats what has been sacrificed to an idol has fellowship with demons. God does not want any humans to have fellowship with demons!