Question:
Can I drink seltzer with a natural lime flavor added to it before davening shacris
Answer:
If there is a need to drink before davening, for example to help you concentrate better etc. then it is permitted, however if it is not for any reason, then the only thing that is permitted is water.
Have a Happy Chanukah
Sources:
Shulchan Aruch 89-3, M:B 89-22, Aruch Hashulchan 89-23, Peninei Halacha pg. 56, Piskei Teshuvos 89-17.