Go by your body. I drink tea every night before bed with milk during my fasting period. I’ve lost a bunch of weight! If you’re not showing the progress you want, cut it out. Otherwise it’s probably fine
The FAQ gives a good explanation on this. Which is pretty much—it depends on what your fasting goal is. Appetite correction <50kal shouldn’t trigger appetite, but if the goal is hormonal than even some zero calorie drinks like coffee can affect your fast.