Can I buy say xxx water bottle, remove their label, replace it with a private/personalized label and then sell to a private buyer?

If the bottle or the design of the bottle is not protected by a patent then you should be able to resell the bottle with your own label.

The answer is: "it depends". As an initial matter, it is unclear from your statement of the facts whether or not the owner of "xxx water bottle" and "their label" has any trademark rights in their water bottle and/or label. If not, then perhaps your strategy will not run afoul of U.S. trademark law. However, U.S. trademark law allows for registration and protection of any distinguishable trademark. It turns out, that even the shape of a water bottle can be distinctive enough for registration. For example, Perrier is a well-known and distinctive brand of carbonated water and they hold numerous trademarks for the Perrier name and their associated carbonated water. But, Perrier also owns U.S. Federal Trademark Registration No. 1,400,594 which is a "design only" trademark registration for their distinctive bottle having a tear-drop shape and green in color. So, as you can see, if you were merely to slap your label on a Perrier water bottle having "removed their label" and "replaced it with a private/personalized label", Perrier would have an action in trademark infringement based at least on Registration No.1,400,594, if not perhaps other trademark registrations and unfair competition laws. More importantly, one has to ask the question: why would you want to "remove their label" and "replace it with a private/personalized label and then sell to a private buyer" in the first place? If you are purchasing a branded bottle of water, you are paying a premium for their branding and trademark. You need an example? Take a bottle of Dasani water. Suppose it costs $1 for a 16 oz bottle of Dasani water. The plastic bottle and cap itself cost a few pennies, say one nickel. The water is virtually free (at least out of my kitchen sink tap). So, you are paying somewhere in the region of $0.95 for the name of "Dasani" on your water bottle. If you plan on throwing away the Dasani label, you are throwing away 95% of your capital outlay at this point in time, based on the exemplary numbers I have provided. It seems much more cost effective and profitable for you to purchase unlabeled water bottles of a generic nature that you could apply your labels to. Alternatively, if you are trying in some way to trade off of the good will and brand name associated with the "xxx water bottle", for example any branded water bottle, the U.S. trademark and unfair competition laws will favor the owner of "xxx water bottle", assuming the owner of "xxx water bottle" has trademark rights associated with their water bottle. As always, you should consult an intellectual property attorney with your specific facts and circumstances so that they can properly advise you so that: (1) you can achieve your business objectives, (2) without infringing the intellectual property rights of others.

Probably, yes. You are not infringing upon the trademark of the seller. There would also be requirements in labeling defined by statute (e.g. ingredients, nutritional data, etc). More facts would be helpful in this analysis.

Yes.

No because you're passing someone else's product off as your own. You may be able to contract with the bottler to purchase the water bottles in bulk with no label or with your label already on them.

Yes.