From what I understand drinks with no sugar or calories at all won't interrupt a fast. Even items around twenty calories probably won't end it either. Electrolyte packets have been the most helpful option for me during those times. When doing a two day fast especially while on glp1 meds I end up needing extra potassium sodium and magnesium and those packets contain artificial sweeteners as well.
For peptides that need to be taken fasted, especially ones like GHRP-2 where food can trigger insulin and weaken the effect, I'm wondering if that includes skipping zero-sugar drinks. I usually have sugar-free sodas or teas in the morning or before bed and figured the lack of calories or sugar meant they wouldn't interfere, but maybe they still cause some insulin response. I'd switch to water if it matters, though I'd rather keep the drinks if they don't make a difference.