I think that drinking liquid minoxidil solution isn't as bad of an idea as it seems but only if you take the correct dosage!
A proper oral dosage of rogaine/regaine solution would be a few microliters, which isn't something you can eyeball. Whatever impurities are in that liquid probably won't hurt you if you're only consuming a few microliters (though maybe the effects could compound if taken over many years? Idk I'm not a doctor)
If you want to consume liquid solution orally please dilute the solution first so that it is easy to measure. Mix 1ml of rogaine/regaine with 10 to 50ml Vodka or everclear (depending on desired strength) and measure out this diluted solution with an accurate graduated pipette or dropper
Also, I highly recommend against consuming more than 5mg of oral minoxidil per day. This is a medication for hypertension. Actually, it's usually only used in cases of severe or treatment resistant hypertension because newer antihypertensive drugs tend to be safer with less side effects. 10mg is a dosage used to treat hypertension - if you've got a normal blood pressure taking this dosage for hair loss will have cardiovascular side effects!
Also, be very careful if using both oral and topical minoxidil simultaneously. Topical minoxidil has a very low systemic absorption but if you're using a lot of it this can be equivalent to a small to medium dose of oral minoxidil and taking a large dose of oral minoxidil on top of this could be asking for trouble