A personal reusable drink bottle (water bottle, thermos, tumbler) that you carry with you; often used for eco- and cost-saving reasons.
毎日マイボトルを持って行くと、ペットボトルのゴミを減らせる。
Bringing your own bottle every day can reduce PET bottle waste.
マイボトルに温かいコーヒーを入れて出勤した。
I put hot coffee in my bottle and went to work.
会社のロッカーにマイボトルを置いておけるので便利だ。
It's convenient because I can keep my bottle in the office locker.