I'm only commenting on this because you asked me to. GuitarRox's answer is correct.
Getting oral hsv1 from sharing drinks is absolutely correct. It's very unlikely to happen - it's a very inefficient way of transmitting herpes.
It's a great way of transmitting colds, flus, covid, strep, etc., though, so sharing drinks, eating utensils, flasks, and the like just isn't a good idea.
67% of people under 50, and about 80% of those over 50 have oral hsv1, and the vast majority of people never get a single symptom. Undoubtedly, you've kissed someone who has it. I don't say this to freak you out, but to inform you that it's just really hard to avoid if you don't already have it.
If this type of anxiety isn't new for you, talk to your doctor about it. There are treatments available that can really help.
I by no means mean to belittle your worry, but 80 percent of the population has herpes simplex 1. Oral herpes. Kids have it. If you haven't developed a sore, you probably don't. Your anxiety is likely getting the better of you. Checking, wondering, needing to reassure yourself are signs your anxiety is running away with you. And we start to 'feel' things when we do that. If you get a sore, go to the drug store and get the topical over the counter ointment they sell for it. Really, this is not serious in any way. But unlikely that you got oral herpes from sharing a flask for seconds. Work on your anxiety as the issue here.