Mayor Bloomberg’s edict to forgo (expensive, unfluoridated, landfill-clogging) bottled water is easy to follow; our taps produce delicious water, fresh from the Catskills. But what about carbonation? Soda-Club USA’s soda-maker ($89 at Sterling Electronics, 369 Kingston Ave., nr. Carroll St., Crown Heights; 718-756-9840) makes seltzer from tap water; fill the kit’s reusable plastic bottles, snap them into the holster, and pump a button several times until your beverage is good and bubbly (kids, particularly, love the burpy sound it makes). For more ways to avoid the plastic-bottle glut, click ahead.