The question is too general and I can’t answer it without knowing the full details. Probably, they are suspecting evil eye from one of you and that is why they asked everyone to drink from the glass and then they use the remains in that glass to wash them with it!
Recently my family called some sufi sheikhs at home and they were reading the full Quran on my mom and sister. What they did was before they started reading they had a glass of water and every body was drinking from it. I know what they do was a bid’ah and I dont like but my question is what do you say about such gathering? Is it permissible and give me some advice towards them and how I can convince my family?