Pineapple (and some other fruits) seem to have a positive effect for many men but it's not known if there are specific things that make women's vaginal fluids taste 'nice'.
Perhaps we should consider why you feel the need to change how you taste? Are you under the impression that you don't taste nice or has a partner suggested that things aren't quite right downstairs for you?
Most men love the taste of women and there would have to be something significantly wrong for the average guy to not want to go down on a girl. So do you really need to improve on nature?
As a general rule, vagina's don't smell like roses or taste sweet like candy. As long as it is in good health, it should smell and taste pleasant to most people. If it doesn't in spite of your genitals being in good health, then it just may be that your partner isn't into the natural smell and taste of women.
To ensure that you smell and taste your best, try avoiding high protein foods and certain vegetables. Have a search online for other suggestions. Make sure you cleanse regularly but avoid using soaps and other chemicals. You want to make sure your genitals have a neutral PH level.
Finally, if you don't think you smell or taste as you should, do consult a GP to ensure that you don't have any yeast or bacterial infections.