I am a 29 year old female. I’m in pretty good shape. I work out at least 3 times a week (moderate-high activity). Most lunches I bring to work consist of mainly fruit. For example: 1 apple, 1 pear, 1 orange, grapes, nuts, crackers and cheese. Is this lunch healthy in that it’s giving me enough calories? Is too much fruit bad for me because of the sugar content?
It is impossible to say whether or not one meal is adequate or not without knowing the rest of your day and more info about yourself. Here is an excellent calorie calculator which will calculate your daily caloric needs based on your height, weight and activity level.
For the second part of your question, it is true that fruit do contain some sugar, but I personally believe that the benefit derived from the vitamins and minerals they provide far outweighs any drawbacks from their sugar content.
FYI, fruit generally have ~10 grams of sugar in one serving. This is compared to 39 grams in a 12 oz can of Coca Cola, 29 grams in a 2 oz. Snickers bar, and 24 grams in 1 serving size of Ben and Jerry’s Chocolate Chip Cookie Dough ice cream (interestingly, the serving size is 104 grams, so 24 out of the 104 grams is sugar).