Hi Connor. I've replied to this post twice and it all seems to have vanished.
Simply add 1% to the drinking water. We bought some large syringes and sucked up the required amount. The capacity of the drinker needs to be known of course. You can't use metal drinkers as the acidity of the vinegar, even at 1%, takes the zinc plating off. It doesn't stop water from freezing.
We have stopped using ACV. The benefits are doubtful and it's a hassle and expensive. We give them fresh fruit and greens instead.