Chickens

Ants need water too ya know? Also... depending on the bottle, what was once in it etc... it could have a smellable or something you can't detect on it that they are trying to get at. Ants have incredible sense of smell given that's how they find their way back to the colony.

l'm not exactly sure what they are after but l know that sugary stuff can linger. Water bottles that have had substances other than plain water in them are actually a bear hazard out in the wilderness due to how acute their sense of smell is lol.

lf you just put water in it... might be the make of it or something?

Its cause I'm sweet

Probably accurate. Ants like me for that reason <3