Anal masturbation is wonderful and fun. Going to the hospital because you picked something bad as a lubricant or because you stuck a vegetable up your ass and then it broke, is not fun. It's embarrassing, and really, really dangerous. Please, please, please don't stick unsafe things up your butt. Anything from the vegetable group, particularly a brittle vegetable, is not a thing that is safe to put up your butt. A fruit is not a thing to stick up there either. The same principle applies to lubricants. Vaseline is an ointment. Do not stick it in your butt. Lotions are moisturizers. Don't stick them in your butt. But instead of enumerating badness, I'd rather tell you what you SHOULD do instead. If you're embarrassed, and maybe you live with your parents or something, get some cash and go buy a prepaid Visa card or something. Use that to order a real dildo, and real lubricant. If you also can't have them shipped to your address, have them shipped to a supportive third person, like a friend. Your local university may also have a queer group and put on the occasional sex toy workshop. These are all safer alternatives.