In our local store, they sell brewer's yeast packets in the vitamin section. Might be better than the health food store where they drive you crazy trying to sell you on stuff you don't even want.
ACV is believed to be safe altho a couple people have had stomach issues after drinking it. ACV is supposed to make you really alkaline, and may aid in vitamin absorption by helping with digestion. If lemon water works for you to raise your pH, you don't NEED to do the ACV, they accomplish much the same thing.