What about switching to seltzer you can mix with caffeine powder? If you look you should be able to find a “cola” flavored one which while not the same should at least be an approximation. From some quick googling it appears seltzer still has carbonic acid which ain’t great for your teeth but it’s not as bad as regular soda’s acid-combo [1].

[1] https://espiredental.com/is-seltzer-really-bad-for-your-teet...