Is yeti or thermoflask available in the uk? Metal is definitely the way to go. My now 4 year old broke multiple supposedly unbreakable plastics (Nalgene, camelback, etc). Usually happened when he would drop the bottle and it would just hit a weak spot, I guess. He has not been able to destroy all metal insulated ones. Yeti (in the us at least) will personalize it with your name for a small fee (helps reduced lost bottles or “accidentally” walking home with other kids).